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Elementary, Economic Experiments in Physics 
by Reginald F. Melton 



IV. apparatus guide 



— . . i. — . 



Apparatus Guide 



to 



ELEMENTARY, ECONOMIC EXPERIMENTS IN PHYSICS 



by 
REGINALD F. MELTON 



- i - 
Table of Contents 

Page 
FOREWORD iv 

1.00 MEASUREMENT 



1.10 DISTANCE 

1.10/01 Triangulation Device 1 

1.10/02 Displacement Block 4 

1.20 MASS 

1.20/01 Balance 5 

1.20/02 Box of Weights 9 

1.20/03 Microbalance 11 

1.30 TIME 

1.30/01 Ticker Tape Timer 12 

1.30/02 Alternative Ticker Tape Timer (Blue-Print) 15 

1.40 FRAMES OF REFERENCE 

1.40/01 Relative Motion Frame 22 

2.00 FORCES AND MOTION 

2.10 INTRODUCTION TO FORCES 

2.10/01 Wire Extender 23 

2.10/02 Wire Spring 27 

2.10/03 Rebound Apparatus 29 

2.10/04 Spring Balance 31 

2.10/05 Puck 34 

2.10/06 Friction Tube with Stand 36 

2.20 MOTION 

2.20/01 Simple Cart 39 

2.20/02 Cart (Blue-Print) 47 

2.20/03 Inclined Plane - 52 

2.20/04 C Clamp 53 

2.30 FORCE AND MOTION 

2.40 MASS 

2.40/01 Inertial Balance 55 

2.50 ACTION, REACTION AND MOMENTUM 

2.50/01 Elastic Collision Runway 57 



- ii 



Pa & e . 

2.60 CIRCULAR MOTION 

2.60/01 Centripetal Force Apparatus 59 

2.70 WORK AND ENERGY 

2. 70/01 Dynamo/Motor 61 

2.70/02 Dynamo /Mo tor (Blue-Print) 74 

2.70/03 Simple Machine 79 

3.00 WAVE MOTION 

3.10 NATURE OF WAVE MOTION 

3.10/01 Ripple Tank 82 

3.10/02 Ripple Tank Accessories 92 

3.10/03 Stroboscope 96 

3.20 INTERFERENCE AND DIFFRACTION 
No further requirements 

4.00 OPTICS 



4.10 PROPAGATION, REFLECTION, REFRACTION 

4.10/01 Light Source with Base 98 

4.10/02 Slit/Aperture Combination 99 

4.10/03 Mirrors and Electroplating 101 

4.10/04 Optical Board with Pins 104 

4.10/05 Optical Prisms 

(Rectangular, Triangular and Semi-circular 106 
Prisms) 

4.10/06 Refraction Model Apparatus 109 

4.10/07 Screen with Holder 111 

4.10/08 Filter (Red) 112 

4.20 DIFFRACTION AND INTERFERENCE 

4.20/01 Simple Diffraction Slits 113 

4.20/02 Adjustable Diffraction Slit (Blue-Print) 116 

4.20/03 Simple Diffraction Holes 118 

4.30 FURTHER OPTICAL PHENOMENA 

4.30/01 Multiple Slit 119 

4.30/02 Lens Holder 120 

4.30/03 Interference Strips 122 



- iii 



Page 
5.00 ELECTRICITY 

5 . 10 ELECTROMAGNETISM 

5.10/01 Dry Cell Holder with Cells 123 

5.10/02 Bulb Holder with Bulb 128 

5.10/03 Switch 129 

5.10/04 Multipurpose Coil with Cores 131 

5.10/05 Compass 136 

5.10/06 Magnetizing Coil and Magnets 138 

5.10/07 Tangent Galvanometer 143 

5.10/08 Magnetic Field Apparatus 146 

5.10/09 Magnetic Field Apparatus with Multipurpose Coils 149 

5.10/10 Moving Coil Galvanometer 153 

5.10/11 Moving Coil Galvanometer with Multipurpose Coils 159 

5.10/12 Moving Coil Galvanometer (Blue-Print) 162 
5.20 DETECTION AND PRODUCTION OF ELECTRICITY 

5.20/01 Neon Bulb Holder with Bulb 168 

5.20/02 Electricity Tester 169 

5.20/03 Resistor Holder with Resistor 170 

5.20/04 Chemical Cell 171 



- iv - 

FOREWORD 

'Triple E Physics' is basically a package consisting of four guides: 
Student Guide, Teacher's Guide, Apparatus Guide and Administrator's Guide. 

The Apparatus Guide is fundamental to the whole program. The apparatus 
it describes has been developed specifically for Developing Countries in the 
realization that their economies are very limited, and that by necessity their 
schools have not only limited laboratory facilities, but also stringent financial 
resources. Apparatus has therefore been designed for economy, for ease of 
operation under limited laboratory conditions, and for ease of production under 
local conditions. 

Most of the apparatus can be made with simple handtools, and students and 
teachers are encouraged to make items for themselves, for apparatus development 
can bring both students and teachers into close contact with the realities of 
science, relating science and technology in the simplest of ways. However, 
this does not mean that students and teachers should attempt to produce all 
their own apparatus requirements. It is recognized that teachers have specific 
curricula to follow, and that "class hours" available for such work are very 
limited. It is also recognized that teachers, particularly those in Developing 
Countries, are not well paid, and often augment their salaries with supporting 
jobs, thus placing severe limits on the "out of class hours" that are available 
for apparatus production. It is therefore recommended that actual production 
of apparatus, sufficient to meet the needs of individual schools, should be 
undertaken by local cottage industries. With such industries in mind a few 
alternative blue-prints have been added to the basic designs. 

Details of related workshop facilities, methods of apparatus production, 
Laboratory plans and overall planning are to be found in the Administrator's 
Guide. 



- 1 - 



1. 10,01 Trlanfiulation iw* 



ce 










- 2 - 



(1) Base 




Cut a strip of wood 
(52 x 2 x 0.8 cms) marking 
a horizontal scale with 5 cm 
intervals along the top right 
edge. Make two feet from a 
wooden strip (5 x 1 x 0.5 cms), 
and attach to the lower surface 
of the scale about 5 cms from 
either end. A piece of aluminum 
(3.5 x 0.5 cms) attached to the - 
near end of the horizontal scale 
will serve as a suitable pro- 
jection. 



(2) Vertical Scale 










rn^m^vA 



m 



Cut a vertical strip of wood 
(20 x 2 x 0.8 cms) and attach 
a paper scale to its front 
surface, marking off distances 
every 0.5 cms from the base. 
Attach a support block 
(2 x 1.5 x 1.0 cms) to the 
bottom, rear surface of the 
vertical strip by means of glue" 
The vertical strip and support 
block should now be placed on 
the base, and an aluminum strip 
(8 x 0.5 cms) wrapped around 
the block, bending the loose 
ends into a spring shape beneat 
the base so as to permit the 
vertical scale to move freely 
along the base. 



- 3 - 



(3) Vertical Endpiece 



n W*>\ » 




r\*vCV 



S^r'w 



lo 




The vertical endpiece is almost 
a replication of the vertical 
scale, but with two differences. 
It is shorter (10 cms not 20 cms), 
and requires no scale markings. 
In addition an aluminum strip 
(3.5 x 0.5 cms) is attached to 
the top of the front surface. 



(4) Sliding Projection 




When the triangulation device 
Is used without a vertical 
endpiece a sliding projection 
is required for sighting purposes. 
This may be made by cutting and 
bending an aluminum strip 
(7x1 cm) to slide on to the 
base. 



.- 4 - 



1. 10/02 Displacement Block 




<§) S\a^Jle 



(1) Block 



A block of wood cut to the 
dimensions shown 



(2) Handle 



A screw or nail 



/ 



5 - 



1. 20/01 Balance 



\U5ft-\ 



§^0. 







f 4 -*- 



c*0*c 



(1) Base 



CawoJ^ V-vaQj. 




L JLoo^nc brtA-i' 



o»w 



— ■ Ok 

d±L_ 



m 



x: 



Hut 



Cut the base from softwood. 
Drill a center hole for the 
support screw and four others 
for leveling bolts. Inset nuts 
into the softwood with a sharp 
hammer blow, and glue them in 
with epoxy resin. The diameter 
of the hole should be that of 
the bolt. Gluing is done with 
the bolt through both nuts to 
insure alignment. Two nuts pre- 
vent the bolt from wobbling and 
permit hand adjustment of the 
bolt. 



N\u\- 



- 6 - 



(2) Support 




MdL^ 



(3) Pivot 




?. 



0.5 



^ 



'^W 



Vi 



r- 



Cut the support with notches at 
the top to receive razor blades. 



Split a razor blade in half, and 
glue the two halves into the 
slots in the top of the support. 
The tops of the blades should 
project as little as possible to 
reduce the strain on the blades. 

Drive a steel needle 0.1 cm in 
diameter and 5 cm long through 
a hole 0.5 cm from the top of 
the arm and glue securely in 
position with epoxy, being 
certain it is perfectly hori- 
zontal and centered. 



O. 



- 7 - 



(4) Horizontal Lever 




C>,5 



2- c^s . 



Cut the pointer from aluminum 
sheeting (0.05 cm thick) and 
bend as shown, gluing it to the 
arm with epoxy as close to the 
center as possible. 

Cut the arm of the lever as 
shown, with notches 0.5 cm wide 
and 1 cm deep at 1.5 cm from 
the ends. For a counterbalance, 
bend a piece of aluminum sheet 
(0.05 cm thick) approximately 
2 cm wide into the shape illus- 
trated. The width of the 
counterbalance should be such 
as to prevent it from slipping 
on the horizontal lever. 



(5) Scale Pan 



VA yvs \ y\ Va W\ 



7/W 




Cut an aluminum sheet to the 
appropriate size and bend (see 
dotted lines) it over the pan 
holder framework. The gauge 
of the sheeting is about 
0.05 cm (0.5 mm) . 



- 8 - 



(6) Scale 



K-- -■>■£■ ~H 






Jl_ 



Make a scale out of white 
cardboard and glue it to the 
support so that the tip of the 
pointer just reaches its top 
edge. 



Notes 

(i) The following table gives approximate values for the sensi- 
tivity of the balance under varying loads. Sensitivity is measured 
as the number of milligrams required to cause the pointer to move 
one millimeter under the given load. 



Load in Each Pan 


Sensitivity 


25 gms 

50 gms 

100 gms 

250 gms 

500 gms 


25 mgms/mm 

25 mgms/mm 

6 5 mgms /mm 

200 mgms/mm 

335 mgms/mm 



(ii) The centering point of the pointer is stable under varying 
weight loads so long as weights are placed centrally in position in 
the scale pans. 



- 9 - 



1. 20/02 Box of Weights 




<T) uk^v 



(1) Weights 



•« C^p Scrto 



CD 



Take a box of wet sand, and 
use wooden dowels, or some such 
similar material, to make cyl- 
indrical moulds in the sand 
according to the dimensions 
given below. Heat up some 
lead in a can, and when it is 
molten pour it into the moulds. 
Allow the lead to solidify and 
cool. Then screw into the top 
of each lead cylinder a cup 
screw to serve as a handle. 
The lead cylinders may then be 
filed down until each is the 
desired weight. The number of 
weights required, and the 
approximate size of each mould, 
is indicated below. 











- iU - 








Qu 


Weight 


Dlam. 


Depth 






1 


500 gm 


3.8 cm 


4.0 cm 






3 


200 


2.4 


4.0 






1 


100 


2.4 


2.0 






1 


50 


2.4 


1.0 






2 


20 


1.2 


2.0 






1 


10 


1.2 


1.0 


(2) 


Box 











A block of wood (17 x 8 x 5 cms) 
will serve as the weight holder 
if holes, the same size as the 
above moulds, are drilled into 
the top surface. 



- 11 - 



1. 20/03 Microbalance 



lW.2^ r .\u\ LA* 



S^^^V 



y 6'cA * fo 




(1) Horizontal Lever 



(2) Pivot 



_X 



NT 



(3) Counterbalance 



(4) Support 



(5) ScoJk 



% 




Take a soda straw and cut one 
end to create a small pan for 
specimens (e.g., mosquitoes, 
flies, hair) 

Push a needle through the straw 
close to one end. The actual 
position depends on the size 
of the counterbalance screw used, 

Take a screw which just fits 
into the end of the straw and 
adjust it to obtain a balance 
of the straw. 

Make the support by folding a 
sheet of aluminum as illustrated 

Cut a wooden block to serve as 
the base of the scale, and a 
wooden strip as the vertical 
support. Glue or nail the 
pieces together . 



aid. 



- 12 



1, 3Q/Q1 Ticker Tape Timer 







UU.v 



junpct-r 



(1) Vibrator Unit 



/^u< */" **%^,c &// 




Obtain a household electric 
bell, and remove the vibrator 
unit. 



C2) Vertical Support 




Cut a piece of wood to serve as 
the vertical support, and attach 
the vibrator unit to it with 
screws* 



- 13 - 



(3) Base 




s f _U<V^° 



Cut a wooden base, approxi- 
mately 16 x 6 x 2 cms. Place 
the vertical support on the 
base In such a position that 
the vibrator arm will be 
parallel to, and directly 
above, the line bisecting the 
length of the base. Mark in 
the position of the support, 
and then drill two appropriate 
holes In the base so as to 
facilitate the attachment of 
the support with screws. 



(4) Platform 



Gx^ on la/>aJt- 




Cut the platform from hard 
wood and the side pieces from 
aluminum. Attach the side 
pieces to the platform with 
nails, then with the platform 
in position on the base bend 
the side pieces at the bottom 
to hold the platform firmly 
in contact with the base. 
(A loosely fitting platform 
will result in a poor track 
being recorded on the ticker 
tape) . 

Cut a circular disc out of 
carbon paper, and pierce the 
center so that it may pivot 
freely about a thumb tack in 
the center of the platform. 



- 14 - 



(5) Vibrator Arm 




Pin four more thumb tacks in 
the platform to serve as guides 
for the ticker tape which must 
pass under the carbon disc. 
There must be negligible friction 
between the guides and ticker 
tape. 

Bend the vibrator arm downwards 
so that the endpiece is within 
3 or 4 mms of the platform 
surface. 



Notes 

(i) Most household bells (and hence the modified timer) are 
designed to operate on about 10 volts. However, 2 dry cells in 
series will generally operate the timer. 

(ii) If ticker tape is difficult to obtain, cashiers' paper 
rolls (for cash registers) are generally available, and may be cut 
into strips of suitable width, so long as care is taken to obtain 
smooth straight edges. 




Ciii) For those with some technical knowledge, wishing to 
produce the timer in its entirety (vibrator unit included) an 
"alternative ticker tape timer" design is presented in the form of 
technical drawings . 



1. 30/02 Altern ative Ticker T ap e Time r 



© ®<p)<^ 



© © 




TICKER TAPE TIMER 



HART no. 


PE'oCRtPTtON 


PtMENMON 


QUANTITY 


\ 


BA^B -(fMARRA) woop 


2 0*U5WC.o 


r 


l 


CO\L aiU CO^E - MAGNET WIRE ^OfT tRON 


*c /t>C5"5*"5.o) 


1 


3 


BR\p&e -BRftv* 


O-HM-3 Xt^O 


l 


4 


BR*** Support 


0OfcXZ 5 


I 


5 


STEEL Boer 


0-45M.9 (ViOTiVC) 


4 


6 


BRA« TABLE 


o- 19x5.0*^4, 


« 


J 


TICKER TAPE GUIPE 


tfo.fGxfco 


2 


8 


CKRfcON HOLPER 


(fowm-Z 


1 


s 


TICKER TAPE SCRCvn W nvjT 


<ia64U9 (XxV**) 


1 


10 


VIBRATING ARMMURC 


o-ifixfe-oxe.6 


1 


h 


CONTACT SCREW Vv/ (HUT 


10^5 


1 


i*. 


OATTER^f HOLPER 


0-07 m J M3-0 


2 


13 


B>TTER\ 

COK4TACT SPRihu* - PRAtt *mect 


tf3-2>txkZ 05 VOLT^) 


Z 


14 


OOSX^4V(2 


\ 


19 


woop s>crew 


d«>47*<-2 


7 


lb 


&\Nf^H 


0<8*<M4*4S 


1 


If 


AfMWJVtgfcC VJRFfcRT 


0.iex(-5"xe.4^ 


t 




Part no 


HCfctR tape timer pak\s -\ - 


^CALE 


i 


&A5E-(i*aRka)woop 


II 









- 17- 



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— - 4-7 ~~| l 


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125 



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x 




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Rivet 



PART NO 


TlCKCK TAPE TIMER PART I -IC 


SCALE 


I 


(nkw^)woop Base (* woop scgtvw tounoNl 


1 \ 


to 


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1. i 




APc> fcKftvi Rivn 


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- 03 ('/ )T#K£AJ> 





CDC 



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Part no. 


TICKEK TAPE TIMER PARTS» -9-H -»/ 


bCME 


9 


Ticker tape ^ct?eu) iW nut - &fy^> 


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14 


VlBRKTlNts AKM/aofc£ ~ V\\\-V STEt> *HtET 


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17 


COMTACX SPR\Nli ~ BRASS bHECT 


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PART NO 


TICKER TAPE TIMER PART% -VA6 7 8-ihlfc 


SCAIE 


"5 


BRAVb ©RU>GE 


1 } 


A 


BRA*S SUPPORT 


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(, 


&RAS* TAfcUE 


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7 


TiilK£R TAP1E1 ialHPE 


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8 


CAKfcOW HOLDER 


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COHTACT ^CRCv^ vaj/ HUT 


f- i 


16 


S^RAL *PRm(a- I*U%IC u*RC 


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1 : 1 



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PAKT NO 


TICKER TAPE VJMER PAKE'S -5M2- 


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2 &otTS CLCNG) ( 2BOU5C$i«oRT) ( BR**S 


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SOFT IKON CORE 

^■+8(3/^ thread) 




CMDCMRP 



ST/IND/»BD NUT Tt> F(T 
THREAD »f Oott 



NOTE: COIL IS ft 26 /*M6NET WIRE WITH * 

6 OHM RESVSTAMCE; TWO WIRE5 WOUND 
IM PARALLEL 



PART MO 


TK.KIRTAPE T»M€R PART -Z~ 


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22 - 



1. 40/01 Relative Motion Frame 



/ *- 



3> 



^ / 



O Jl&- t^l<t_c_AiiQrv 




fTXi v Q_cAv o rv 



(1) Base 



(2) Lower Projection 






(3) Side Projection 



Cut the base out of hardboard 
or plywood (35 x 25 x 0.5 cm). 

Take a strip of wood 
(34 x 2 x 0.5), and cut an 
inset (1 x 0.1) along the 
bottom far edge, so that when 
the strip is glued to the base 
the inset will make a groove 
between the projection and 
base. 

Cut a strip of wood 

(25 x 1 x 0.5), and glue to 

the base as shown. 



2.10/01 Wire Extender 



23 - 



(Jv^yx 










(1) Base 




Cut the base out of wood 
(85 x 4 x 4 cms). Make an inset 
along the top of both of the end- 
pieces, and glue a metal roller 
(a cut off nail, 0.7 cm in diam.) 
firmly in each inset using expoxy 
resin. File a small groove in the 
middle of each roller to contain the 
extension wire in position. 

Insert two screws about 3 cms apart 
at the same height in one of the 
endpieces to maintain the wireholder 
in position. 



- 24 - 



(2) Adjustment Device 



(xt ooK- 




2.o 



1 + 



I'O IS" o^~ 



g^&Q^p 










ej^ 






Bore a hole (0.7 cm diam., 3 cm 
deep) into the center of the other 
endpiece. Then take the nut from 
a suitable nut and bolt combina- 
tion (6 cm long and 0.7 cm diam.), 
and inset it over the hole by 
tapping it sharply into the wood 
with a hammer. 

Now drill two holes through the 
bolt, a nail hole (0.3 cm diam.) 
0.5 cm from the bolt head, and a 
wire hole (0.05 cm diam.) 2 cms 
from the bolt head. (A drill press 
will be essential for this process.) 

A nail (5 cms long, 0.2 cms diam.) 
may then be inserted through the 
appropriate bolt hole, which should 
be large enough to permit the nail 
to slide freely in and out. 

A screw of approximately the same 
length as the bolt should be in- 
serted into the endpiece at the 
same height as the bolt, but as far 
to the side of it as possible, to 
serve as a stop screw. 



- 25 - 



(3) Wire Arrangement 



&AW 




flJ&j 




fce»W 



Cut a nail (10 x 0.7 cms) down to 
7 or 8 cms to serve as the wire 
holder, and drill a hole through 
its center to take one end of the 
wire (100 cms of #26 steel wire). 
Attach one end of the wire to the 
holder, and pass the other end over 
the base to the adjustment bolt, 
making sure that the wire sits in 
the groove of each roller. 



Fasten the end of the wire to the 
adjustment bolt by means of the 
appropriate wire hole, and take up 
the slack in the wire by turning 
the bolt. The latter can then be 
held in a set position by lodging 
the bolt nail beneath the stop 
screw. 



- 26 - 



(A) Bridge 




T*- 



^^"^ (Wv«xJV°*\ 



(5) Pointer Arrangement 




Cut and bend the bridge from 
aluminum sheeting, and attach it 
to the top surface of the base (with 
small nails) about 10 cms from the 
wire holder end. The bridge is in- 
tended to provide some protection 
should the wire break, and one 
might in fact prefer a second bridge 
close to the middle of the base. 
The projection from the bridge also 
serves as a rest, and zero position, 
for the pointer. 

Attach an aluminum base plate 
(5 x 3 x 0.1 cms) to the top surface 
of the base about 2 cms from the 
endpiece to which the wire holder 
is attached. 

Cut a small wire plate (2 x 2 x 0.1 
cms) from aluminum or brass, and 
thread a hole in the center to take 
a small bolt. Once the bolt has 
been screwed into the hole cut off 
the protruding end beneath the 
plate, so that when the plate is 
attached to the wire, the bottom 
surface is always smooth. 

The pivot may be an aluminum or 
brass rod (6 cms long, 0.15 cm 
diam.) bent at the end to prevent 
the pointer from slipping. 

Cut the pointer (13 cms long) from 
cardboard, and attach to the bent 
end of the pivot with scotch tape. 



- 27 - 



2.10/02 Wire Spring 




(1) Spring 



v 



* T "b 



Approximately 40 cms of steel wire 
(#26, approximately 0.07 cms diam.) 
should be sufficient to make a 
spring about 10 cms long and 1 cm 
in diameter* 

The most important factor in winding 
the spring is to keep the wire taut 
at all times, and for this the help 
of a brace and two nails (10 cm) is 
invaluable. Drill a horizontal hole 
about 3 cms deep in the bench for 
the free moving nail, and about 
20 cms to the right of this drive 
in a second (fixed) nail. Clamp 
one end of the wire, along with the 
head of the free nail in the jaws 
of the brace, and get your partner 
to hold the other end of the wire 
in the jaws of a pair of pliers, 
keeping the wire taut with the 
assistance of the fixed nail. Turn 
the brace, winding the wire firmly 
around the free nail. The spring 
may be close wound (each turn touch- 
ing the next) or open wound (each 
turn separated from the next by a 
fixed distance). Although the wire 
is wound on a nail of diameter 
0.7 cms, on release from tension it 



- 28 - 



it will tend to expand to about 
1 cm diameter. 

(A spring made from a more 
plastic material such as copper 
wire can be made much more easily, 
simply by winding the wire onto 
the nail by hand.) 








^OtvAA 



- 29 



2,10/03 Rebound Apparatus 







(1) Steel Block 



(2) Lead Block 

(3) Base 



(4) Suspended Spheres 



This will have to be obtained from 
a metal workshop. It is important 
that the end surface should be 
smooth and reasonably polished. 

Heat some lead in a can, and when 
molten pour it into a sand mould. 

Cut the base from wood. Make an 
inset (say 0,4 cms) into the top 
surface to hold the blocks, and 
glue these firmly in position. 

Two spheres (1.2 cms diameter) are 
required, one of lead and one of 
steel , Make the lead on? as usual by 
pouring lead into a mould (cylindri- 
cal) s and then filing it to an 
approximately spherical shape. 
Screw a cup screw into the sphere. 



- 30 - 



For the steel sphere take a ball 
bearing, and attach a cup screw 
by soldering. The two spheres 
should then be connected to one 
another by a length of string 
(50 cms). 



31 



2 .10/04 Spring Balance 




$) OvAir T^W 



(1) Spring 




The method of winding the spring 
has already been described for 
the wire spring, making use of a 
brace (Item 2.10/02) . 

If a 10 Newton balance is to be 
made take #26 gauge steel wire 
(diameter 0.07 cms) and open wind 
it (0.1 cms between each turn) 
into a spring approximately 8 cms 
long and 0.9 cms In diameter. 

If a 1 Newton balance is to be made 
take #30 gauge steel wire (diameter 
0.03 cms) and open wind It (0.1 cms 
between each turn) into a spring 
approximately 8 cms long and 0.6 cms 
In diameter. 

Make a loop on one end of the spring 
(using dog nosed pliers) and a 
straight piece on the other end. 



- 32 - 



(2) Inner Tube 




O Ot^ACV 



y.^Kr> oet^O 



(3) Outer Tube 



oWL 



\ 






Take a hollow aluminum tube 
(length 21 cms, external diameter 
1 cm), and make two stoppers out 
of wood (2 cms long, 1 cm diameter). 
Fix a cup screw into one of the 
stoppers and glue it permanently 
into one end of the aluminum tube. 
Drill a small central hole through 
the other stopper and insert the 
straight end of the spring, bend- 
ing the end over to hold it in 
position. Glue the stopper into 
the other end of the tube. 

Take a hollow aluminum tube (length 
27 cms, internal diameter 1.3 cms) 
and make a wooden stopper (2 cms 
long, 1.3 cms diameter) to fit 
one end of the tube. Fix cup 
screws in either end of the stopper, 
and attach the top end of the spring 
to one of the cup screws, 

/ 




Now, take the combination of 
stopper, spring and inner tube, 
and lower it into the outer tube 
until the stopper lodges in the 
top of the tube. Glue the stopper 
firmly into the tube. 



~ 3 

Notes: 

(i) To calibrate the 10 Newton spring hold the balance vertically, and 
mark the inner tube opposite the lower end of the external tube 
(0 Newtons). Suspend 1,020 gms from the spring and once again mark 
the inner tube opposite the lower end of the external tube. Then 
subdivide the distance between the two marks into 100 equal divisions, 
thus permitting the balance to read from 0.0 to 10.0 Newtons with an 
accuracy of 0.1 Newtons. 

(ii) To calibrate the 1 Newton spring simply suspend a mass of 102 gms from 
the balance and repeat the above process, calibrating the inner tube 
from 0.00 to 1.00 Newtons with an accuracy of 0.01 Newtons. 

(iii) Spring balances are very easily damaged by over extension of the spring. 
It is therefore useful to make some simple device to prevent over stres- 
sing the spring. 

One such method is to tie a piece of magnet wire (diameter 0.05 cms) 
around the inner cylinder, just above the final marking on the scale. 
If the lower perimeter of the outer tube is then tapped gently all 
around It, the magnet wire will be unable to move beyond this point, 
thus preventing over extension of the spring. 

f^^Bgrrriz;...^..i...i... ; i .'.........-«.........,........ 1 ,, ,, [ itt^NWyvAWNM^^ 

N 






- 34 - 



2.10/05 Puck 



& 



V\ 



(SXKV 



& 



e* 



^fl_ 




(1) Base 












W 
^U*. 



Cut the base out of wood (diameter 
10 cms, thickness 0.7 cms). Polish 
and varnish the lower surface on 
successive occasions until it is 
perfectly smooth. 

Drill a small hole (0.1 cms) through 
the center of the base, and drill 
an inset (0.3 cms deep, 0.5 cm 
diameter) over this to hold the 
glass tube (2.5 cms long, 0.5 cms 
external diameter) . Seal the tube 
firmly in position with epoxy resin. 



35 - 



(2) Balloon 




SYrm 



Notes: 
(1) 






A suitable balloon would have a 
diameter of approximately 15 cms 
when inflated, and would be spheri- 
cal in shape (not elongated). In- 
sert a rubber stopper (2.5 cms long, 
2 cms diameter) into the neck of 
the balloon after drilling a hole 
(0.5 cms diameter) through it to 
take the glass tube from the base. 
If necessary hold the balloon firmly 
in position on the stopper by wrap- 
ping string tightly around the neck. 



To prepare the puck for use, hold the base in one hand with your finger 
over the small central hole. Take the balloon in your other hand and 
inflate it. Push the stopper of the balloon as far onto the glass tube 
as possible. The puck is ready for use on a smooth surface (e.g., table 
with glass cover, formica table top, etc.). 



- 36 - 



2.10/06 Friction Tube with Stand 




(1) Tube 



(2) Base 



Take a discarded fluorescent tube 
(approximately 100 cms long, 4 cm 
diameter) , and wash off the internal 
white coating. You will find this 
is easily removed. Fit a cork into 
the bottom of the tube, and seal 
(watertight) it with rubber cement 
or ordinary paint. 

Cut the base out of wood ( 20 x 20 
x 2 cms), and cut an inset (2x2 cms) 
about 1 cm deep into the baae to 
support the wooden upright. 



- 37 



(3) Upright 




cre^*3 



Put wood glue into the inset, and 
then attach the upright (100 x 2 
x 2 cms) to the base with a screw 
from below. Bore horizontal holes 
(0.5 cm diameter) through the up- 
right at regular 5 cm intervals. 



I^sA 



(4) Clamp 




To make each of the clamps take a 
14 cm length of steel strip (pack- 
ing case bands about 1 cm wide 
will do) , and bend into the shape 
shown. Drill a hole (0.4 cm diameter) 
in the center of the straight piece, 
and insert a bolt (3 cms long, 0.4 cm 
diameter) through it. 



- 38 - 



lAprio^ 




The clamp is attached to the up- 
right by means of the bolt and an 
appropriate wingnut. 



Notes: The stand is not an essential requirement for the friction tube for 
the tube could easily be handheld. However, the stand is included 
in the description since it is a useful general item. 



2. 10/01 Simple Cart 



- 39 - 




Vrtv 



- 40 - 



(1) Body 



(2) Spring Device 






tod 






A 



t*^^r 



t 



t 



SCtCu) 



L^CSSSiiSBm' 



nTTCTOTOTC 



D 



V>oy* Kobu 



Cut the body (15 x 6 x 5 cms) from 
a piece of wood. 

Bore a hole from the center of one 
end of the cart to the center of the 
other end, in order to accommodate 
a spring device. The diameter of 
the hole (1.2 cm) should be slightly 
larger than that of the spring 
(0.9 cms). 

Bore holes into the top surface of 
the cart to accommodate six masses 
(see 1.20/02), namely one 100 gm 
mass (diameter 2.5 cms), four 200 gm 
masses (diameter 2.5 cms) and one 
500 gm mass (diameter 4.0 cms). The 
holes should not be so deep as to 
cut into the horizontal hole for the 
spring. 

Wind some 40 cms of steel wire 
(#26, diameter 0.07 cms) into an 
open spring (separation of each 
turn about 0.4 cms) approximately 
8.5 cms long and 0.9 cms diameter 
(see details under 2.10/02 and 
2.10/04). Straighten out one end 
of the spring into a spike and the 
other to a horizontal loop. 

Cut a wooden rod (10 cms long, 
0.9 cms diameter), and attach the 
spring to one end by means of the 
spike and epoxy resin. Attach a 
rubber stopper (approximate 
diameter 2.5 cms, length 1.5 cms) 
to the other end of the rod. 



- 41 



(3) Spring Release System 




$fc 






Bore a hole into the bottom of the 
cart so that it meets the bore hole 
for the spring close to the rear 
end of the cart. Then insert a 
screw to anchor the end of the 
spring. 

Ideally, two or three alternative 
springs of varying thickness and 
length should be made for trial 
purposes. The ultimate spring 
selected will be such that if two 
identical carts (one carrying 
3 times its own weight) are placed 
end to end, and the spring device 
on one cart is then released, both 
carts will move apart a sufficient 
distance at uniform velocity to 
enable a measure of their initial 
separation velocities to be re- 
corded. 

Screw a metal plate (brass, steel, 
etc.) onto the front of the cart 
so as to just overlap the top of 
the borehole for the spring. 

File a small notch around, the wooden 
rod on the spring device, close to 
the stopper. 

It is thus possible to compress the 
spring into the bore hole, and hold 
it in position by means of the notch 
and metal plate. 

Bore a vertical hole (diameter 0.5 
cms) into the top of the cart, near 
the front end, so that It meets the 



42 - 







V*e VW* 




^////mmm - s y 



i.- 



:. 




r*Ws;*«v*^ 



SY**\ 



v&* 



horizontal bore hole for the spring. 
A small wooden rod (releasing rod) 
inserted into this hole, and pressed 
against the horizontal rod of the 
spring device itself, will release 
the spring from its state of com- 
pression. ( The need to have the 
diameter of the spring bore hole 
slightly greater than that of the 
spring and attached rod should now 
be clear, for it is an essential 
requirement if the spring is to 
be released) . 

Cut the releasing rod to the di- 
mensions illustrated. The rod 
should be capable of moving freely 
in its bore hole, but at the same 
time it shouldn't be so loose 
that it is easily lost. To 
realize this condition thread a 
thin piece of steel wire (#30) 
through the rod so that it acts 
as a spring contact between the 
sides of the rod and the .bore hole. 



- 43 - 



(4) Ticker Tape Bracket 




!«- 



JS 



n 



*J±L 



if. 



CNV^S 



n 



jt 



i-^*i 



U — a-fe- 



iii. 



-** 



,|« L.1 



Cut the ticker tape bracket from a 
sheet of metal (brass, aluminum) 
which should be reasonably rigid. 
Make slits near the end to take 
the ticker tape, and slots along 
the bottom to enable the bracket 
to be attached to bolts (0.3 cms 
diameter) at the rear of the cart, 
Wingnuts should be used to fasten 
the bracket In position. 



-I 



jo- 



.n 



- 44 - 



G^t-> 







<u\<$ju 



The purpose of the bracket Is to 
insure that ticker tape attached 
to the cart is in line with the 
guides of the timer during any 
experiment, thus reducing friction. 
Two typical examples are illustrated 
when carts are mutually repulsed 
from one another (Case i) , and when 
a single cart runs down an inclined 
plane (Case ii) . 



CuS^I'm) 







(5) Chassis 







Drill two horizontal holes 
(0.5 cms diameter) through the 
cart to permit passage of the 
front and rear axles. 

Cut the chassis from metal (steel, 
packing case bands, 15 x 1.5 cms). 
Drill 5 holes along the length 
of the strip, 2 (diameter 0.3 cms) 
to coincide with the centers of 
the axle holes and 3 to enable the 
strip to be attached firmly to the 
body with screws. 



- 45 - 




(6) Wheel System 




T~ 



^uxlc- 



■> 



K> 



?Z12 *- ^ 



\v*<<A 



The axles of the cart will In fact 
pivot in the chassis holes and not 
on the wooden holes through the 
cart, thus reducing friction. 



Cut the four wheels from the ends 
of two wooden spools (approximately 
4 cm In diameter and 1 cm thick) . 
Fill the spool holes (0.5 cm 
diameter) with wood putty and allow 
to dry hard. 



Cut two lengths of wire (approximate- 
ly 0.2 cm diameter, 10 cms long) 
from wire coathangers to serve as 
axles for the cart. 

Drill holes, slightly less than 
2 mm in diameter, in the exact 
center of each wheel, and insert 
a little epoxy resin in the holes. 



- 46 - 



Notes : 

(i) 



(ii) 



Tap the end of one axle into one 
of these holes, checking carefully 
to insure that the axle is at right 
angies to the wheel (thus avoiding 
subsequent wheel wobble). 

Insert the axle through the body of 
the cart, and attach a second wheel 
by the same process. Repeat the 
procedure with the remaining two 
wheels and axle , thus providing the 
cart with front and rear wheels. 

Make small spacers for all four 
wheels from masking tape (1 cm wide) , 
in each case wrapping it around 
the axle (next to the wheel) until 
it produces a cylindrical spacer 
1 cm long and 0.5 cm in diameter. 

A little soap applied to each axle 
will serve as a lubricant between 
the axle and chassis contact points. 



Adjust the total weight of the cart to 400 gms by cutting some wood off 
the under surface of the body, and drill the holes in the top surface 
somewhat deeper if necessary. 

A superior wheel system can be made if a metal lathe and a reasonably 
skilled technician are available. With this in mind a technical draw- 
ing of an almost identical cart, with a modified wheel system, is in- 
cluded next. 




2 ao/oi Co.rV 




PART NO 


pCSCVUPTioW 


Pimen j<ons 


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-, 49- 




PART MO 


CART PACTS 1-7 


SCAUC 


1 


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2 BRAS*> WKEEU$ and £ 6R*^> ?CRCU)S 


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PART NO 


CAkl VART<> A-SG-7 


SCALE 


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1 ticker tave holper - aluminium 


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- 52 - 



2.20/03 Inclined Plane 




CWd 



(1) Plane 



(2) Chuck 



Cut the plane from 5-plywood 
(150 x 18 x 2 cms) if possible, 
since this does not warp so readily. 
Two metal strips may be placed 
along the sides of the 
plane to prevent subsequent dis- 
tortion. Mark a 15 cm scale along 
the top edge of the plane to check 
the chuck position, and hence indi- 
cate the inclination of the plane. 

Make 4 wood chucks, each 18 cms 

long and 3 cms wide, with depths 

of 0.5, 1, 2 and 5 cms respectively, 



- 53 - 



2,20/04 C Clamp 



Lf.QsCt\\ pr 




^K>*0 



(1) C Bar 



With the assistance of a heavy duty 
clamp hammer an iron strip (14 x 
2 x 0.3 cms) into the shape shown. 
If necessary apply heat to assist 
in the bending process. Drill a 
hole (0.6 cms diameter) through the 
center of one of the end pieces, 
and make a thread on it for the 
adjustment screw. 



- 54 - 



(2) Adjustment Screw 



&.W- 



\ 



i 



i » 






(3) Head 



l.o 

•* > 



llfljf 



i 



toxs^V 




iWi 



feo\V- 



Obtain a heavy bolt (4 to 6 cms 
long, diameter 0.6 cms). Drill 
a hole (approximately 0.2 cms 
diameter) through it close to the 
flat end. Insert a nail (0.2 cms 
diameter, length 5 cms) through 
the hole to serve as the adjustment 
screw handle. 

The clamp will work well without a 
head, but the pointed end of the 
bolt is likely to damage any sur- 
face to which the clamp is attached. 

Take a soft iron rod (1 cm diameter) 
and cut of f a length of 0.8 cms using 
a hacksaw. Drill a hole (diameter 
0.6 cms) along its axis to a depth 
of 0.5 cms. 

Take the bolt, and file a groove 
around it at about 0.4 cms from the 
pointed end, making the end spheri- 
cal in shape. Push the shaped end 
of the bolt into the head, and tap 
the perimeter of the head lightly 
with a hammer so that it closes 
loosely over the shaped end of the 
bolt. 



- 55 - 



ia.s" 










ot^V 



(2) 



(1). Fixed Platform 



Cut a simple platform (12.5 * 5.5 
x 2.0 cms) out of wood. 



- 56 - 



(2) Vibrating Platform 
/ ~ 




Cut a second platform out of wood, 
identical to the first. In the 
center of the top surface of the 
platform make an inset (0.3 cms 
deep, 5 cms diameter) using a 
chisel. Then bore a hole (1.5 cms 
diameter) at the center of the 
inset right through the platform. 



(3) Flexible Strips Drill suitable holes in the ends of 

two steel strips (each 30 x 1.2 
x 0.05 cms approximately) and 
attach to the platforms as indicated. 
Each strip could be made from a 
double strip (not single) of packing 
case band material. 

(4) Side Plates Cut 4 steel plates (5.5 x 1.2 x 

0.2 cms). Drill a hole in each 
about 1 cm from either end, and 
screw on to the sides of the plat- 
form. The side plates prevent 
sideways motion of the flexible 
strips where they are in contact 
with the sides of the platform. 

Notes: Adjust the weight of the vibrating platform and its 2 side plates 
to 100 gms, by cutting the inset deeper if necessary. 



- 57 



2. 50/01 Elastic Collision Runway 




(1) Base 



-£^ 



vO 



.?*. 



"& 



O.c 4 



t <•- 



- VlCvw^ 



tf- 



*•> 



1 



*s>r~- 






VW™ 



>"\X 



, 1 J^-SW 



-5.0—1 



?» 



SV 



Cut the base from an aluminum sheet 
about 0.15 cms thick, which is 
reasonably rigid, but can still be 
bent, A slit is required to take 
the ball bearing support and flanges 
to hold the runway in position. 
Bend the base as shown at an angle 
of 30°. 



(2) Runway 



The runway is simply a plastic 
ruler, 30 cms long with a typical 
groove down its center. Bend the 
base so that the runway is held 
firmly in position by the base 
flanges at either end. 



58 - 



(3) Ball Bearing Support 










Cut the plate from aluminum 
(0.2 cms thick) which is thick 
enough to be threaded. Drill two 
holes (0.4 cms diameter) as shown, 
and cut a thread (0.45 cm) so that 
the holes will take 0.45 bolts. 



Utv\<Or\^A\ 




lQ a s W t 



6>tvte- & KuywJo^ 



Belt- 



f \cJt of t*x\\ UaWna S^^otA' 



The plate is attached to the base 
by means of a bolt (1.5 cms long, 
0.45 cms diameter), a nut, a washer 
(1.2 cms diameter) and a wingnut. 
The head of the bolt is flattened 
somewhat by filing so that it does 
not create two big a protrusion 
beneath the base. 



Jj*.pf-es&.*°A 




rlvAY^V" 



Y\<^ 



The support screw is made from a 
bolt (2.0 cms long and 0.45 cms 
diameter) . File the pointed end 
of the bolt flat, and then drill 
a depression into the surface to 
act as a support for ball bearings. 
Thread the bolt into the plate, and 
hold it firm by means of a nut. 
Finally tie a meter thread to the 
head of the bolt, and suspend a 
screw from it, so that it will 
serve as a plumbline. 



- 59 



2.60/01 Centripetal Force Apparatus 




CWw 



2 



Wo\& 



cr— 




y 



(1) Holder 



Take a glass tube with an internal 
diameter of about 0.6 cms, and cut 
off a length about 13 cms long. 
(Simply file a sharp line around 
the tube and snap it with your 
hands). It is convenient to cover 
the glass tube with a length of 
rubber tube (bunsen burner tubing) 
which permits a better hand grip 
on the tube. Put the ends of the 
tube in a hot flame to smooth off 
the edges. This will prevent the 
cutting of the string as the stop- 
per is whirled around. 



- 60 - 



(2) Stopper and Thread 








Take a rubber stopper (approximate- 
ly 2.5 cms long, 2.5 cms diameter) 
and drill a hole (0 # A cms) alon^ 
its axis. Fasten one end of a 
strong length of string (1 meter 
long) firmly to a paper clip, and 
thread the string through the hole 
in the stopper. Plug the hole 
with a wooden dowel (2.5 cms long, 
. 5 cms diameter) so that the 
string is held firmly in position. 



Thread the string through the holder, 
and tie a loop at the extreme end 
(to hold the spring balance) , and 
attach a paper clip about 20 cms 
from the loop to serve as a marker. 



2.70/01 Dynamo/Motor 



- 61 - 







©' 



<xSA_ 



flr<wx'WK 



3) fo\-e rt^cjs. 



£> AA S-ff^ s 



62 - 



(1) Base 



(2) Armature 




Vvlorrtie/* KoJ 












(U 










— »3, 




Cut the base out of wood 
(20 x 15 x 3 cms) . 

Take a wooden block, and drill a 
vertical hole (diameter 0.8 cm) 
through its center so that it can 
support a steel axle (15 cms long, 
0.7 cms diameter). The latter may 
be a very long nail with the head 
removed. 



Take a sheet of aluminum (13 x 
4 cms) and with the help of an appro 
priate series of end projections 
and holes make it into a cylindri- 
cal container (4 cms tall, 4 cms 
in diameter) . 



rrot<4cV o( v' 



Place the container on the wooden 
block so that it encircles the 
axle. Take two wooden rods 
(4 x 2 x 1.2 cms) and stand these 
against opposite walls of the 
container. Now fill the remaining 
space in the container with 4 cm 
nails (or similar soft iron materi- 
al) packed closely side by side 
and parallel to the axle. 

Cover the ends of the nails (not 
the wood) at both ends of the con- 
tainer with epoxy resin, so that 



- 63 - 




pexe\LMr><\ 



fnvv\^v-t-< ^ c 



oK 




(3) Pole Heeds 



Wodk^ \SckM 




nvf 




\\jt<xa 



when it dries the nails are welded 
together into a solid soft iron core 
penetrated along its axis by a 
steel axle protruding 4 cms at one 
end and 7 cms at the other. Remove 
the aluminum container and the 
wooden rods. You now have the 
core of your armature. 

Take a coil of magnet wire (#26) 
and wind as much as possible into a 
coil around the core, making sure 
that you have about 10 cms of both 
ends left free, having made the 
coil. Temporarily twist the loose 
ends around the long end of the 
axle. The resistance of the coil 
will be approximately 5 ohms . 

The pole heads are made in very 
much the same way as the armature 
core. Two open ended containers 
are required this time, one cylin- 
drical (5 cms diameter, 4 cms long) 
and one a rectangular cube (7x7 
x 4 cms) . The cylindrical one is 
placed inside the rectangular one, 
and the two held apart by two 
wooden rods (2x1x4 cms). 
Just as when making the armature 
core, pack the space between the 
two containers with 4 cm long nails, 
packed parallel to the axis of the 
cylindrical container. Cover the 
nail ends at both extremities of 
the containers with epoxy resin. 
When this has dried remove the two 
containers and the wooden rods. 
You will now have two pole heads. 



- 64 



To 



-M 



5o 



f$^ 




Place the pole heads on the base 
in the positions illustrated, and 
attach them firmly to the base with 
the help of epoxy resin. 

Complete the system with 4 very 
strong magnets (7x1x1 cm) laid 
parallel to one another (North Pole 
touching North Pole) across the gap 
between the pole heads. The magnets 
may be purchased, or made as des- 
cribed in the electromagnetism 
section. 




J^V<*n<& 



foW **>* 



- 65 - 



(4) Axle Supports 



O.g 



A-.O 




Make two axle supports out of 
brass sheeting (0.2 cms thick), 
drilling one hole (0.8 cms 
diameter) in the upright portion 
to take the axle, and two holes 
(0.3 cms diameter) in the base 
portion to take two screws. 



fY\cvsV\A 




3o-o 



.1 







Slide the supports on to either 
side of the axle, and attach them 
firmly to the base of the apparatus 
in the positions shown. 



The axle may be held firmly in 
position by winding masking tape 
(not scotch tape) around the axle 
next to, and just outside, the 
supports. 



- 66 - 



(5) Commutators 




DC 




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(i) To make the DC commutator take a 
piece of brass tubing, and cut it 
to make two halves. 

Take some epoxy resin, which is a 
good insulator, and coat all the 
inner surfaces of the two halves 
with resin about 0.1 cm thick. 

Rotate the armature coil until it 
is in a vertical plane, and then 
attach the two split halves to the 
axle so that thesplit between the 
halves is in a horizontal plane. 
If the epoxy resin is thick enough 
it will not only attach the split 
halves firmly to the axle, but will 
also insulate the two halves from 
one another, and from the axle 
itself. 



67 - 



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Take the two loose wires from the 
armature coil and, after cleaning 
the ends with sandpaper, solder 
one to one split half and the other 
to the other split half. 



Cut two identical contacts out of 
thin brass sheeting (0.1 cms thick) 
as shown. Attach these to the 
base of the apparatus with screws, 
so that they are in spring contact 
with opposite sides of the split 
halves . 

The DC commutator is now complete. 



- 68 







fmciS 










G^wc.* 







(ii) To make the AC commutator take a 
a piece of brass tubing and cut 
two identical rings from it. 

Temporarily remove the axle support 
and slide the two rings on to the 
axle. Coat a length of axle 
(0.5 cms long) with epoxy resin 
about 0.1 cm thick and slide ring A 
into position over this. The epoxy 
resin should be such as to insulate 
the ring from the axle as well as 
to hold it firmly in position. 

Ring B is soldered to the axle 

about 0.5 cms from ring A. Solder 

insures good electrical contact 

between the ring and axle. Two 

contacts, identical to those made 

for the split halves, should be 

cut from brass, and attached to 

the base so that each is in spring 

contact with one of the rings. 
> 
Connect ring B electrically to one 

of the split halves (B f ) by solder- 
ing a very short length of magnet 
wire (#26) from ring B to the axle 
and split half B 1 to the axle. 
Don't forget to clean the ends of 
the magnet wire with sandpaper 
prior to soldering. 

Connect ring A electrically to the 
other split half A' by soldering 
a length of magnet wire (#26) from 
one to the other. 



The AC commutator is now complete. 



- 69 - 



(6) Terminals and Electric Wiring 




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Drill 4 holes through the base to 
take 4 terminals, two to serve as 
an AC outlet and two as a DC 
outlet. 

Make each terminal as follows. 
Insert a brass bolt (2.5 cms long, 
0.3 cms diameter) through the hole, 
and attach two nuts, one to serve 
as a locking nut and one as a 
terminal nut. 

It is of course very nice to have 
fairly large nuts which can easily 
be adjusted with the fingers. Such 
nuts are probably best made on a 
metal lathe. The nuts might both 
be 1 cm in diameter, with the thick 
ness of the terminal nut being 
0.5 cms and that of the locking 
nut 0.2 cms. 

In some localities It Is cheaper 
to purchase terminals on the local 
market. Check the availability of 
such items as Fahnstock clips which 
can replace the above 



- 70 - 




Take some magnet wire (#26) , clean 
the ends with sandpaper, and then 
connect the terminals to the con- 
tacts as illustrated, fastening 
the wire beneath the screw of the 
contact and beneath the locking nut 
on the terminal. 






- 71 - 



(7) Driving Wheel System 



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Take a wooden spool (3 cms diameter, 
2.5 cms long) and fill the central 
hole with wood putty. When the 
latter is perfectly dry drill a 
new hole (0.7 cms diameter) along 
its axis so that it will just fit 
on the armature axle. Cut a rubber 
strip (2.5 by 9.5 cms) from an old 
car inner tube, and nail it around 
the perimeter of the spool. Tem- 
porarily remove the appropriate 
axle support, and attach the spool 
firmly to the axle with epoxy resin. 

Cut a wooden support (12 x 5 x 
4 cms) for the driving wheel, and 
locate it on the base in the position 
shown. Cut a slight inset (0.2 cms) 
into the base to hold the bottom 
of the base firmly, and put some 
wood cement in the inset. Fasten 
the support firmly in position 
with the help of two wood screws 
passing through the base of the 
apparatus. 



- 72 - 










Cut a wooden disc (15 cms diameter, 
approximately 1.5 cms thick) to 
serve as the driving wheel. Cut 
a rubber strip (1.5 x 44 cms) from 
an old car inner tube, and nail it 
around the perimeter of the disc. 
Drill a hole (0.8 cms diameter) 
through the center of the disc, 
and pass a nail (0.7 cms diameter, 
6 cms long) through it to serve as 
a pivot. 




&. 






Take another wooden spool (2.5 cms 
diameter and 2.5 cms long) and a 
screw (4.0 cms long). Drill a hole 
along the axis of the spool so that 
the spool fits loosely on the screw, 
but cannot slip over the screwhead. 
Screw the spool onto the driving 
wheel about 4 cms from the peri- 
meter. Locate washers either side 
of the spool to permit it freedom 
of motion. You now have a handle 
for the driving wheel. 

Washers should be similarly placed 
on the pivot, either side of the 
driving wheel. 



- 73 - 



vS^X)potV 




Finally, hold the driving wheel 
tight against the axle spool, 
and use the pivot to mark the best 
position to locate it permanently 
in the support. This will be at 
a height of approximately 10 cms 
on the support. Drill a horizontal 
hole (diameter 0.7 cms) into the 
support, and fix the pivot firmly 
in the hole with epoxy resin. 

Your dynamo/motor is now ready for 
operation. 



- 74- 



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- 78- 



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2,70/03 Simple Machine 




(1) Base 



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Cut the base from a piece of wood 
(24 x 24 x 2.5 cms), providing the 
apparatus with a firm base. 






80 - 



(2) Frame 




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Attach two uprights (63 x 4 x 4 cmi 
each) firmly to the base with wood 
cement and screws. 

Sit the crosspiece (24 x 5 x 4 cms 
on top of the uprights, and fasten 
firmly with wood cement. 

Mark two scales of 30 cms each on 
paper, and fix to the uprights 
in the positions shown. 



(3) Pulley System 



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Take a spool (approximately 4 cms 
diameter) and cut off the two ends 
The two extremities may be attache 
to one another with wood cement to 
form a pulley. Make two more 
pulleys in exactly the same way. 

Bore two horizontal holes (0.7 cms 
diameter) into the crosspiece in 
the positions marked A and B, and 
use nails (0.7 cms diameter) to 
fix two of the pulleys to the cros 
piece in these positions. Make su 
that the pulley hole is big enougti 
to permit it to move freely on the 
nail. Place washers either side 
of each pulley. 



- 81 - 



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The third pulley must be able to 
lift masses. With this in mind 
cut two steel bands (packing case 
bands, 2.5 x 1 cm) and drill holes 
(0.8 cms diameter) to take the 
pivot nail (0.7 cms diameter). 
Fasten the free ends of the two 
bands to a short wooden rod 0.8 cms 
diameter, 1.2 cms long) with epoxy 
resin. 

Now drill a hole (approximately 
0.3 cms) through each pulley, 
fairly close to its perimeter, 
to take a nail intended to serve 
as a "jamming rod 11 . Drill corres- 
ponding holes in the crosspiece 
and the steel bands of the third 
pulley arrangement, so that any 
single wheel might be locked in 
position by insertion of a "jamming 
rod" through the pulley and into 
the corresponding hole in the cross- 
piece, or steel bands. 

Take a 2 meter length of string and 
attach one end to a screw in the 
crosspiece. Wind the string around 
the three pulleys as illustrated, 
keeping the string taut by sus- 
pending masses from the third pulley 
and from the free end of the string 
Since this simple machine has been 
designed to illustrate problems 
due to friction a coarse string 
(as opposed to a smooth nylon 
string) is preferred. 



- 82 - 



3.10/01 Ripple Tank 



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- 83 - 



(1) Basic Tank 




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To make the frame of the ripple 
tank (60 x 60 cms) , take 4 pieces 
of wood, each 60 cms long and of 
cross section approximately 3.5 
by 3.5 cms. Out of each side 
cut a single length approximately 
2.0 by 2.0 cms. (A small circular 
saw is useful in performing this 
task) . You now have 4 large 
pieces of wood to make the lower 
frame, and 4 small pieces to 
make the upper frame. 

The end pieces of the lower 
frame are cut (as illustrated) 
so that they may be firmly joined 
together with wood cement. 



Cut a glass plate (0 6 3 cms thick) 
so that it will sit on the ledge 
of the lower frame. 

Cover the edges of the glass, and 
the inner edges of the lower and 
upper frame with a waterproof 
cement as illustrated. An 
asphalt or rubber based cement 
is ideal. Sit the glass on the 
ledge of the lower frame, and 
hold it in position by placing 
the upper frame on top of it. 

The whole frame may be held 
together by clamps, or nails 
tacked temporarily through the 
two frames, until the cement is 
dry. 



- 84 - 




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(2) 


Beach 





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You now have a basic tank with 
an inner and outer frame in- 
suring the tank is leak proof. 



The beach is any device which 
will cut out unwanted reflections 
from the sides of the tank. One 
of the most effective , and durable 
of beaches is made from soft pine 
wood (packing case material) • Mai 
the beach rather like a picture 
frame so that it sits on the 
glass surface of the tank, and 
fits snugly within the upper 
frame. 



The most important aspect of the 
beach is the angle of the surface 
as it slopes downward from its 
outer to inner edge. The dimen- 
sions of a cross section to cope 
with water depths varying from 
0.5 to 1.5 cms is illustrated. 



- 85 ■ 



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Smooth the surface of the beach 
with fine sandpaper (leaving a 
smooth, but porous, surface), 
but do not varnish. Wetting 
the surface of the beach at 
the commencement of a series 
of experiments makes the damp- 
ing of the waves most effective. 

Prevent the beach frame from 
floating by making 4 metal clips 
to attach to the corners of the 
ripple tank frame. Pivot each 
clip around a nail so that the 
beach can readily be released. 



Beaches may be made from many 
alternative materials. Fine 
wire gauze is frequently used 
for this purpose, but on its 
own is not as effective as the 
wooden beach. However, if the 
surface of the wire gauze is 
covered with cotton cloth an 
extremely good beach is created. 
The only problem is that the 
cloth must be replaced periodi- 
cally. 



4*.\ ^(xuie. U^'m*- 



5^' 5' 



- 86 - 



(3) Outlet 




A water outlet is not absolutely 
essential, but it does make the 
draining of water from the ripple 
tank so much simpler, and prevents 
the spilling of water all over 
the floor. 

Cut a short length of aluminum 
(or brass) tubing, say 1 cm in 
diameter and 5 cm long. Bore 
a horizontal hole of the same 
diameter into the ripple tank 
frame, close to one of the tank f s 
corners, so that drainage may be 
assisted by tilting the tank 
towards the corner. The bottom 
edge of the outlet hole should be 
at the same level as the top sur- 
face of the glass (or just a 
little below). 

Seal the metal tube into the 
horizontal hole with a water- 
proof cement. Bore a hole 
(0,9 cms diameter) partway 
into a rubber stopper using an 
electric drill (not a cork borer) . 
Fit the stopper on the tube, thus 
controlling the outflow of water. 



- 87 



(4) Legs 







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Cut 4 identical legs (60 x 3 x 
2 xms) out of wood, and drill 
and chisel a slot (2 x 0.5 eras) 
in the top of each to permit 
adjustment. Make 4 insets 
(0 . 3 cms deep) in the frame to 
hold the legs firmly in a verti- 
cal position. Finally, drill 
a horizontal hole (0.45 cms 
diameter) through the lower part 
of the outer frame (that is be- 
neath the level of the glass) at 
the middle of each inset. Attach 
each leg to the frame with a bolt 
(0.45 cms diameter, 3 cms long) 
passed through the hole in the 
frame and the slot in the leg. 
Fasten it with a wingnut. 



- 88 - 



(5) Lamp Housing 

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The size of the lamp housing 
will be dependent on the size 
of the contained lamp. In this 
case the lamp utilized was a 
220 volt, 100 watt lamp with its 
filament 8 cms from the socket. 
Ideally the filament should be 
a straight line, but a slightly 
bent filament such as that illus- 
trated will serve the same purpose, 

To make the housing for the above 
lamp take a sheet of aluminum 
(35 x 16 cms) and cut an aper- 
ture (5x5 cms) from its center. 
Roll the sheet into a cylindrical 
shape, and hold it in position 
by means of bent end pieces. 



n=f 





- 89 - 








Lar^p Odc-kxJ 



Cut a circular endpiece (11 cms 
diameter, 0,4 cms thick) from 
hardboard or plywood and attach it 
to the base of the container 
with very small nails. Drill a 
central hole in the endpiece 
to facilitate the placement 
of the lamp and electrical 
socket. Complete the housing 
by making a lid out of aluminum 
sheeting. Drill a small hole 
(0.2 cms diameter) in the lid, 
such that it is in line with 
the filament. 



(6) Lamp Support 







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The vertical component of the lanq 
support is made, and attached to 
the ripple tank, in very much the 
same way as the legs. The verti- 
cal component itself should be 
65 x 3 x 2 cms with a slot 7 x 
0.5 cms cut near to its bottom 
end to permit adjustment. 



fcvyne 



- 90 - 



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Cut a rectangular hole 
(2x1 cms) in the top of 
the vertical component to 
take the horizontal component 
(48 x 2 x 1 cms). Fasten the 
two firmly together with wood 
cement. A triangular piece of 
wood may be glued between the 
two components to make a 
stronger junction. 




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In order to attach the lamp hous- 
ing to the horizontal component of 
the support make two brackets 
from steel strips (packing case 
bands) as illustrated. Cut 4 
horizontal slots in the upper 
part of the lamp housing and pass 
the steel strips through. Fasten 
the loose ends of the brackets 
together with a folded piece of 
aluminum or packing case steel. 
Then slide the brackets over the 
horizontal component of the lamp 
support. 



- 91 



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Obtain two steel strips (30 x 1 
x 0.1 cms) / or stiff coathanger 
wire to serve as the arms of the 
vibrator. Attach a glass sphere 
(diameter approximately 1.5 cms) 
to the end of each arm using 
epoxy resin. 

Make the vibrator clamp from two 
strips of wood (each 7x2x1 cms) 

Drill a hole (0.45 cms diameter) 
through both to take a bolt* In- 
sert the bolt (diameter 0.45 cms, 
length 2.5 cms) through the lower 
strip, and then attach the strip 
to the frame with two screws. 
Sit the top strip on top of the 
first, and fasten it in position 
with the bolt and wingnut. The 
vibrator arms may now be clamped 
firmly between the strips of the 
clamp, being held at the middle 
of the arms. This insures the 
maximum possible period of 
vibration. 



- 92 - 



3.10/02 Ripple Tank Accessories 




- 93 - 



(1) Depth Marker 



Mark off the end of a 10 cm 
length of wire in half centi- 
meter intervals (0-2 cms). 
This is used to determine the 
depth of the water at the 4 
corners of the ripple tank, 
and makes the levelling of the 
tank simpler. 



(2) Straight Line Source 




Cut a 40 cm length of a wooden 
rod (approximately 2 cms 
diameter) . Bore holes into 
both ends and insert long 
nails (or metal rods) to prevent 
the rod from floating around 
in the ripple tank. 



(3) Straight Barriers 




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Make the barriers out of wood. 
The following size barriers 
are desirable: 

1 Barrier 40 x 2.5 x 1 cm 

2 Barriers: 15 x 2.5 x 1 cm 
2 Barriers: 10 x 2.5 x 1 cm. 
1 Barrier: 5 x 2.5 x 1 cm 
Prevent the barriers from floating 
by nailing thin strips of lead 
along the sides and base. 



M, 



(4) Curved Barrier 



(5) Rectangular Plate 



(6) Curved Glass Plate 



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Cut about 55 cms off a smooth 
surfaced hose pipe approximately 
2 cms diameter. The pipe may 
be curved into any desired arc. 

Take a sheet of glass (0.4 cms 
thick) and mark out two sections 
(each 25 x 15 x 0.4 cms) with a 
glass cutter. Break the glass 
along the marks by hand. The 
two sheets may be set one on top 
of the other in water, thus 
creating a plate of thickness 
0.8 cms. 

Two curved glass plates (0.4 cms 
thick) may be made by cutting 
along the lines indicated. 
Smooth off the edges with a 
sandstone. The two plates may 
be used one on top of the other 
in the ripple tank making a single 
plate of thickness 0.8 cms. 
Equally well the plate may be 
made from a sheet of plastic 
(1 cm thick) . Simply use a 
hacksaw to cut along the lines 
indicated, smoothing off jagged 
edges with sandpaper. 



- 95 - 



(7) Vibrator Mass 








Cut a soft iron bar to the 
approximate dimensions of 
11 x 2 x 0.3 cms, adjusting 
the size so that the bar weighs 
approximately 50 gms. Place 
the bar in a strong clamp, and 
use a hammer to bend it in half 
so that it becomes two parallel 
bars about 0.3 cms apart. 
Drill a hole (0.2 cms diameter) 
in the middle of the top bar, 
and make a thread (0.2 cms 
diameter) in the hole. A 1 cm 
long bolt screwed into the hole 
will make it possible to clamp 
the bar onto the ripple tank's 
vibrator arm. 



~ 96 - 



3.1Q/Q3 Stroboscope 



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(1) Wheel 




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Cut the stroboscope wheel from a 
piece of hardboard about 0.3 cms 
thick. Make 12 equally spaced 
slits in the perimeter of the 
wheel. Drill a finger hole at 
a distance of 3 cms from the 
center of the wheel, and a 
pivot hole (0.5 cms diameter) 
at the center of the wheel. 



- 97 - 



(2) Handle 



(3) Pivot 







\^W>4 



The handle is simply a wooden 
dowel (2 cms diameter , 
25 cms long) . Drill a hole 
(0,45 cms diameter) through 
one end of the handle to take 
the pivot bolt. 

Obtain a bolt (0.45 cm diameter, 
4.5 cms long) to serve as the 
pivot for the wheel. Insert this 
through the wheel, a spacer 
(diameter 3 cms, width 1.5 cms) 
a locking nut and the handle. 
Use the locking nut and a 
wingnut to hold the handle 
in a fixed position on the pivot. 



- 98 - 



4,10/01 Light Source with Base 




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(1) Lamp Housing 



(2) Base 






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This is precisely the same 
lamp housing as that designed for 
the ripple tank (3.10/01). All 
that is added is a base. 

Cut the base from a piece of 
plywood (21 x 11 x 0.5 cms). 
Cut 4 side strips (2.5 cms 
wide, 1 cm deep), two of which 
will be 11 cms long while the 
other two will be 16 cms long. 
Make sure that they will hold 
the lamp housing firm, and 
then nail into position. 



- 99 



4.10/02 Silt/Aperture Combination 




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Cut the slit (0.1 cms width) 
and apertures (0.1 cms diameter) 
in any suitable thin sheeting 
(metal, bakelite, cardboard) 
so long as the slit and apertures 
have clean cut edges. If the 
material used is relatively 
rigid, a small wooden block 
will provide adequate support ♦ 
If the material tends to flex 
under its own weight a frame- 
work, such as that indicated 
below, will be required for 
support. 



- 100 - 



(2) Framework 







tttJSU 



Make each sidepiece of the 
frame from three strips of 
wood, so as to create a thin 
groove (as illustrated) between 
the two inner strips. Then 
slide the metal sheet between 
the two parallel grooves, 
finally fitting the top and 
bottom strips of the frame 
with wood cement, or small 
nails. 




The thickness of the bottom 
strip should not be much more 
than 0.5 cms, as there is a 
tendency for this strip to 
cut off a desirable portion 
of any light path. 



101 - 



4. JO/0 )_ Mirrors and K lee Lropla ting 



HoU 







VVJ' ' 



fv 



,A» 






i , —■■ 




(1) Mirror 




Cut a sheet of brass (10 x 2,5 
x 0.1 cms) on a metal 
guillotine (to be found in your 
nearest metalwork shop)* If 
the metal sheet is cut with 
bench sheers some distortion 
is almost certain to result, 
thus lowering the quality of 
the mirror. If the mirror 
is to be curved, bend it over 
a smooth, curved, wooden block 
until the mirror becomes the 
arc of a circle of radius 
8,5 cms. 

Polish the metal strips first 
with coarse carborundum paper, 
and then with successively 
finer and finer grades, taking 
care at each polishing to 
remove the deeper marks of the 
previous polishing* 

Obtain a mirror finish by 
polishing the surface with a 
soft cloth and metal polish* 



- 102 - 



(2) Holder 





^AoiVc YcxAO- 



> p\c^Si*<~ ^H^- 



Cut a slot (0.2 cms wide) in 
a wooden block (2x2x2 cms) 
Line the slot with plastic 
tape to prevent the wood from 
scratching the surface of the 
mirror to be held. 



Alternatively, take a packing 
case band (approximately 
7x2 cms) and bend it into 
a triangular shape. Curve 
the endpieces and cover them 
with plastic tape to protect 
the mirror surface. 



Note: 

Brass mirrors must be cleaned with metal polish before each usage. This 
process may be eliminated if the metal surface is electroplated. The procedure 
to be followed is described below. 

(i) Procure a plastic, or glass, container about 15 cms deep and 10 cms in 
diameter, and fill it with a nickel solution (e.g., Gleamax and Levelbrite) . 

(ii) Wash the polished brass mirror in caustic soda (soap) to remove grease 
and rinse with clean water. Grip the brass mirror in a crocodile clip, attached 
to an electrical lead, and suspend the brass mirror in the nickel solution. The 
mirror may be held in position by wrapping the electrical lead (by which it is 
suspended) around a wooden dowel bridging the container. 

(iii) Suspend a nickel plate in a similar fashion from a second electrical 
lead. We now have an anode (nickel plate) , a cathode (brass mirror) and an 
electrolyte (nickel solution) . 



- 103 - 

(iv) Connect the anode to the positive terminal and the cathode 
to the negative terminal of a 6 volt battery, and pass a current through 
the nickel solution for 15 to 20 minutes. The quality of the final surface 
will depend primarily on the quality of the initial polished surface, prior 
to electroplating. 







104 - 



4,1 0/04 Optical Board with Pins 



® 



Of^ioJl feevcV^ 



T\i\% u^'TTK 0\ 



*W<5> 




(1) Optical Board 



(2) Steel Pins 



This is simply a piece of 
hardboard about 40 x 40 cms 
into which pins can be readily 
stuck. Normally a plain 
sheet of paper will be placed 
on top of the hardboard to 
facilitate the recording of 
experimental observations. 
The Refraction Model Apparatus 
is such a piece of hardboard 
(40 x 40 cms). 

Make the pins (7 cms long, 
0.1 cm diameter) from any 
appropriate steel (e.g., 
cycle spoke's) simply by 
cutting off the desired 
length, and sharpening one 
end on a file. 



- 105 



"Cut a pencil to a length of 
6.5 cms. Remove the pencil 
lead with the help of a steel 
pin. Coat the steel pin with 
epoxy resin, and slide it into 
the space originally occupied 
by the lead, so that, instead 
of the pencil lead, a steel 
pin protrudes from the end. 
Cover the sleeve with a white 
coat of paint. 



- 106 - 



4,10/05 Optical Prisms and Lenses 





1 /~1 K^-cA Ov *\ <»^Va \ OlT ""-_ 




s * ' 





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CX.W 

t"WV ^ c 








All the above prisms are made 
from plastic (acrylic) sheets 
about 2 cms thick by pre- 
cisely the same process 
indicated below. 

Take a sheet of plastic, 
and mark out the shape of 
the desired prism with a 
sharp point. Draw a 
parallel set of lines about 
0.5 cms outside the initial 
marking . 

Using a fine toothed saw 
carefully cut the plastic 
down ta the outer markings. 
The cut produced will have 
very jagged edges, the plastic 
showing a tendency to chip. 
This is normal, and should 
cause no concern. 



- 107 - 




PlJbu 






*v>x 



Kc0a> 



The next step is to remove 
the rough edges from the prism, 
reducing its size to that of 
the inner markings . For this 
purpose place a coarse sheet 
of carborundum paper on top 
of a smooth surface (e.g., 
a strong glass sheet). Then 
smooth down the surfaces of 
the prism by rubbing the 
latter on the carborundum 
surface. 

Repeat the process with 
successively finer and finer 
grades of carborundum paper, 
taking care at each rubbing 
to remove the deeper marks 
of the previous rubbing. 

Finally, replace the 
carborundum paper by a 
sheet of plain paper. Drop 
a little metal polish on the 
paper, and repeat the rubbing 
process. The surface produced 
will be highly polished. 

The rubbing and polishing 
process is repeated with all 
the surfaces except that 
surface which will normally 
be in contact with the table 
top during experimentation. 
This surface is smoothed with 
carborundum paper, but not 
metal polish, thus leaving 
the surface sufficiently 
rough to scatter light. 



- 108 



Note: 

Plastic is not as hard as glass, and is therefore more easily scratched 
and damaged. From time to time it is therefore necessary to repolish the 
surfaces with metal polish, as described above. 



- 109 - 



4,10/06 Refraction Model Apparatus 



ouna&rvs 



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(1) Platform 



3^> 



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hirvvei 



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(A>^^ 




Take a sheet of hardboard or 
plywood measuring 40 x 40 
x 0.5 cms. Cut a 7 cm strip 
from one side, and shape the 
newly cut edges back at an 
angle of 45 degrees as 
illustrated. Reattach the 
7 cm strip to the platform 
with very small hinges 
avoiding the creation of a 
gap between the strip and 
main platform. Shape the 
free edge of the 7 cm strip 
to an angle of 45 degrees. 
This shaping insures good 
contact between the strip 
and the table. 






110 - 



(2) Supports 



(3) Ramp 




Books, or blocks of wood, 
may be used to elevate the 
platform to different 
heights above the table top 
(say to heights of 2 and 
4 cms) ♦ 

Cut two triangular shapes 
out of a piece of wood 
about 2 cms thick. The 
height of one triangular 
shape will be 5 cms and 
the other 3 cms, while both 
will have a base 12 cms long. 

The groove is best cut with 
the help of a saw. 



(A) Ball Bearing 



A ball bearing (2.5 cms 
diameter) is required for 
use with the apparatus. 



- Ill - 



4.10/07 Screen with Holder 



Sc 



t $J£.<\ 




H*t<kr 



(1) Screen 



(2) Holder 




Make the screen from a stiff 
piece of cardboard, say 
25 x 15 cms. It is very 
convenient to have a front 
white surface and a rear 
black surface. This may be 
achieved by sticking appro- 
priate sheets of paper on 
the two surfaces. 

Bend a length (8 cms) of 
packing case steel as shown 
and nail it to the side of 
a wooden block (4x4x4 cms) 



112 - 



4. 10/08 Filter (Red) 



|0cA>vf 




ft-UOfYAQ- 



(1) Cellophane 




Test different strips of 
red cellophane for 
suitability by noting 
what parts of a spectrum 
can be seen through the 
cellophane . The cellophane 
cutting out almost all colors 
other than red will be most 
suitable. 



Lc\V»>pW*v! 



(2) Frame 



»•*" 



Oo 



i 



\o. 



Cut two pieces of cardboard 
to the shape indicated, and 
stick (or clip) a suitable 
piece of red cellophane 
between the two pieces. 



- 113 - 



U. 20/01 Simple Diffraction Silts 



pA VvksXadW 

3Ut 





- 114 



(1) Fixed Slits 



(2) Adjustable Slit 



Take an exposed strip of 
film (or a slide coated with 
colloidal graphite) and draw 
a straight line across it 
using a razor and a straight 
edge as a marker. The 
width of the slit may be 
increased, if desired, by 
drawing the razor over the 
same approximate line two 
or three times. 

A double slit may be made in 
an almost identical way. 
Simply hold two razors face 
to face instead of one, and 
draw the line across the 
film with the two razor 
blades pressed closely 
together. The space between 
the slits may be increased, 
if desired, by holding the 
blades at an angle to the 
vertical as the double 
line is drawn against the 
straight edge. 

Hold two razors against a 
metal strip so that the 
edges of the blades are 
almost touching and are 
parallel to one another. 

The combination may readily 
be converted to an 
adjustable double slit 
by using epoxy resin to attach 
a needle (3 cms long, 0. 1 cm 
diameter) at right angles 



- 115 - 



to the metal strip, and then 
holding the two blades 
(against the strip) as close 
to the needle as possible. 

Note: 

A somewhat more sophisticated adjustable slit, based on the same principle 
as the above item, is included next* However, it is anticipated that this will 
only be produced by those possessing particular technical skills. 



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- 117- 




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- 118 - 



4.20/03 Simple Diffraction Holes 



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(1) Metal Strip 



Take a strip of aluminum 
(10 x 2.5 x 0.1 cms) and 
drill 4 holes (diameters 
approximately 0.1 f 0.08 f 
0.05, and 0.02 cms) in it 
at regular intervals. 



119 - 



4,30/01 Multiple Silt 




(1) Framework 




Take 4 strips of wood 
(0.5 cms thick) to make 
the basic framework. Make 
regular identations down 
the middle of the top and 
bottom strips of the frame- 
work, the indentations being 
0.4 cms apart. 



(2) Nails 



<£* 



-.i 




Take a handful of nails (abou 
0,2 cms in diameter) and cut 
off the top ends to produce 
a uniform set of nails, each 
4 cms long. Tap the nails 
into the bottom strip, 
positioning them in the 
indentations. Then press 
the upper strip onto the 
upright nails, using the 
indentations on the upper 
strip for guidance in 
positioning the nails 
parallel to one another. 
Finally, attach the side 
pieces of the framework 
using very small nails or 
wood cement. 



02 Lens Holder 



- 120 - 




(1) Base 



Cut the base out of wood 
1 cm thick* Make two 
insets (0*5 cms deep and 
3 cms apart) in the base to 
take the two uprights. 
Drill a small hole (0,2 cms 
diameter) in the middle of 
each inset. 



(2) Uprights 




Set the uprights (each 12 
x 2 x 1.0 cms) in the base 
insets with wood cement, 
insuring a firm joint by 
screwing very small screws 
through the base into the 
upright. 



I^V u^ 



121 - 



(3) Top Plate 




-To e ?Ufc 



UlorloS* 



Cut the top plate (7 x 1.0 
x 0.1 cms) out of aluminum 
or brass. Drill a small 
hole (0.2 cms diameter) 
at a distance of 1 cm 
from each end. Attach 
the top plate to the upright 
with very small screws. 



Note: 



A lens may be held in any position on the upright by means of rubber bands. 



- 122 - 



1 »- \WQ3 Interference Strips 



/g\ ^Q^dl^L 




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(1) Metal Strip 



(2) Handle 



This may be of any desired 
metal. In this instance 
two are specifically 
recommended, namely copper 
and steel (packing case 
bands) . Make the strip 
14 cms long. 

The handle is made from 
wood. Cut a slit (4 cms 
long) down the middle of 
the handle with a saw. 
Cement the metal strip 
into this inset with 
epoxy resin. 



- 123 



5.10/01 Dry Cell Holder with Cells 



£^<A P; 



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CX$ PUs 



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(1) Base 



Cut the base out of soft wood, 
and use a curved chisel to 
make a long groove (about 
0.5 cms deep) in the surface 
to hold the dry cells in 
position. 




c*» 



- 124 - 



(2) Cells 



(3) Endpieces 




09 co\ ©oaf) 



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Tot C^ivMfn&^O 



Place 3 dry cells in series 
the groove of the base* The 
groove should be from 1 to 
1*5 eras longer than the 3 
cells placed end to end, thu 
allowing room for the placin; 
of contacts between the cell 
and for adjustment of the 
screw in one of the endpiece; 

Cut the end pieces from a br 
sheet (0.2 cms thick). Dril 
3 small holes (0.2 cms diame 
at the base of each endpiece 
to facilitate attachment to 
the base with small screws. 
Place the dry cells on the 
base to determine the height 
of the mid point of the dry 
.cells, and then drill an 
inset (0.9 cms diameter, 
0.2 cms deep) at this height 
in one endpiece, and a hole 
(0.4 cms diameter) at the 
same height through the othe 
endpiece. Thread the newly 
drilled hole to take the 
adjustment screw (2 cms long 



<SeKU 



- 125 - 



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(4) Terminals 






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The adjustment screw described 
may have to be adjusted with 
the help of a coin, or some 
such device. A much more 
convenient adjustment screw 
could be made by a technician, 
or anyone familiar with a 
metal lathe, cutting the head 
and screw from a single piece 
of brass. The base would be 
made from a separate nut, 
firmly attached to the screw 
by damaging the threads at the 
end. 

Make 4 terminals from brass 
bolts (approximately 2.5 cms 
long, 0.3 cms diameter) . Two 
nuts are required, one to 
serve as a locking nut and 
one as a terminal nut. 

Somewhat better nuts, which are 
more easily adjusted with the 
fingers, may be made by anyone 
familiar with a metal lathe. 
The terminal nut should be 
0.5 cms thick, while the 
locking nut should be much 
thinner (0.2 cms). The 
diameter of both should be 
1 cm. 

In some localities it is 
cheaper to purchase terminals 
on the local market. Check 
the availability of such 
items as Fahnstock Clips which 
can replace the above. 



TOw\\Y\s*ocK v\\o 



z 



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(5) Contact Plates 




IrvS^aX 




Make 4 Insets (0.2 cms deep) 
at equal Intervals underneath 
the front side of the base to 
take the bolt heads of the 
terminals. Insert the k 
bolts from below, and attach 
the locking nuts and terminal 
nuts . 

Use copper wire to attach t lie 
end terminals to the endpieces , 
fastening the bare ends of the 
wire beneath the terminal 
locking nuts and brass 
endpieces. Similarly attach 
a length of copper wire 
(15 cms long) to each of the 
middle terminals. 

Cut two tli in brass sheets into 
circular discs (1.5 cms 
diameter) , and use a nail 
head or punch to make a 
central inset (1 cm diameter, 
0.2 cms deep). Solder the 
two plates to the bare ends 
of the wire attached to the 
two middle terminals. The 
contact plates are placed 
between the first and second , 
and second and third cells, 
thus enabling the apparatus 
to provide an external circuit 
with 1.5, 3.0 or 4.5 volts 
according to the terminals 
connected to the circuit. 



._ (fU.cYrvc^A v'xfo.jJA' 



- 127 - 



Notes : 

(i) So long as the adjustment screw is not tightened too tightly the 

c.c \] s will remain firmly in the base groove. However, should any problem 

occur (e.g., due to bad 
aJ ignment of the adjustment 
screw) the cells could be 
held more firmly in place 
by means of clips made from 
packing case bands. 




- 128 - 



5.10/02 Bulb Holder with Bulb 




T 5 



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a^- 



(1) Base 



(2) Bulb Holder 



(3) Terminals 



Cut the base out of wood 
(7x3x1 cms approximately). 

Obtain a bulb holder (porcelain 
or metal) from the local 
market, and screw it onto the 
base. The holder should take 
a variety of local bulbs 
(e.g., 1.1 volts, 2.5 volts 
and 6.2 volts) . 

These are the same as the 
standard terminals described 
for the dry cell holder. Use 
magnet wire to connect the 
bulb and terminals, not 
forgetting to clean the ends 
of the wire. 



5.10/03 Switch 



- 129 - 




\^\ vrvvAOu^ 



(1) Base 



(2) Terminals 



(3) Contact 



Cut the base out of wood 
(7x3x1 cm) . 

These are the same as the 
standard terminals described 
for the dry cell holder/^ \o\v\) 

Screw a brass screw into 
the wood (2 cms from one 
terminals) and connect it 
to the terminal by nean» of 
a short length of copper wire. 



- 130 - 



(4) Spring 



Q' 






2° 







C©a.Tg.cX / r / 



Make the spring out of a 
piece of brass sheeting 
(5 x 1 x 0.1 cms). Drill a 
small hole (0.3 cms diameter) 
in one end of the spring so 
that the terminal bolt will 
pass through it, and hold the 
spring in position by 
fastening the terminal locking 
nut. Cut a wooden head 
(1 cm diameter, 0.5 cms thick) 
and attach it to the free end 
of the spring with epoxy resin. 



- 131 - 



5 ♦10/04 Multipurpose Coil with Cores 




(1) Spool 



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oo^ 



\JLJJ - 



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F 






The size of the spool is not 
critical, but it does affect 
the spacing and size of multi- 
purpose coil holders used on 
the magnetic field apparatus 
and moving coil galvanometer 
described later in this section. 

Wind 10 layers of magnet 
wire (#22) on to the spool, 
and then pass the loose ends 
of the wire through the last 
loops to prevent the coil 
unwinding. The winding of a 
coil by hand is a very tedious 
process, and it is well worth- 
while making a simple winding 
device to facilitate this 
(see notes below this item) . 



- 132 - 



(3) Endpieces 



f 

3 

I 




<- 2 



Cut two endpieces from a piece 
of wood (0.4 cms thick), and 
cement them on to either end 
of the spool. Drill appropriate 
holes (0.6 cms diameter) in the 
endpieces so that the hole 
through the spool also extends 
through the endpieces. 



(3) Terminals 




Make two terminals (see 
details under 5.10/01). Drill 
two small holes (diameter 0.3 cms) 
in the bottom of one endpiece 
and attach the terminals in the 
usual way. It will be found 
that the terminal bolt need 
only be 1.5 cms long in this 
case. 

Clean the ends of the two wires 
from the spool coil, and 
fasten them under the locking 
nuts of the respective 
terminals. Make sure that it 
is possible to see the way in 
which the wire from each 
terminal begins to wind 
around the coil, for this makes 
it possible to determine the 
direction of the current 
around the coil, and hence 
the direction of the magnetic 
field produced. 



- 133 - 



(4) Core 






on* 



x 



I 



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CoH^ 



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W 



Take a nail or bolt of diameter 
0.5 cms, and cut off a length 
of 3.8 cms next to the head. 
Drill an inset (0.4 cms deep, 
1 . cms diameter) over the 
hole in the endpiece containing 
the terminals. 



to^ 



TV\Ufli. 



PoUWaJ 




Cut an iron plate (2 x 3 x 
0.3 cms), and drill a hole 
(diameter 0.4 cms) through its 
center. Thread the hole, and 
similarly put a thread (0.4 cms 
diameter) on the end of the 
core. Slide the core into the 
hole in the spool and attach 
the iron plate (polehead) to tfc 
end of the core. 



Note: 



(i) The polehead is added to the core when uniform magnetic fields are to 
be produced (e.g., in the magnetic field apparatus and in the moving coil 
galvanometer) . 



- 134 - 



(ii) The following is one of many possible methods of winding the 
multipurpose coil with magnet wire* Pass a bolt (4 cms long) through the 
hole in the spool and hold it in position with two nuts at the other end* 
The length of the bolt should be such that the second nut only just bites 
onto the thread of the bolt, thus leaving an inset which may be used as a 
pivot point* It may be necessary to adjust the length of bolt thread available 
to the nuts by inserting washers between the nuts and the spool (or between 
the bolt head and spool) , 



\ 



o 



. 



ge.ll- 






N«As 



4J 



/j 



\ 



/ 






PiVot 



feewcji 






Hammer a nail (3 cms long, 0.3 cms diameter) through a strip of wood 
(10 x 5 x 1 cm approximately), and nail the strip to the side of a bench so 
that the nail protrudes as a pivot . Hammer a second nail (10 cms long, 
0,5 cms diameter) into the bench at the same height as the pivot nail, but 
about 50 cms from it. 



135 - 







-^fr 




Wrap the first turns of the magnet wire onto the coil, and tie it 
so that it will not slip. Then grip the bolt head firmly in the jaws 
of a brace. If necessary file the edges of the bolt head to insure a 
good grip with the jaws. Pivot the free end of the spool by means of 
the inset in the nut and the protruding nail. 

Get your partner to hold the loose end of the magnet wire over the 
second tape in such a way that the wire is kept taut during winding. Now 
with the wire under tension wind the wire onto the spool by turning the 
brace. 



136 - 



5, 10/05 Compass 



Q) Cop 




cxi^_ 



(1) Base Cut the base from a thin strip 

of wood (0.3 cms thick) so as 
to form a disc (2.5 cms 
diameter) . Although less 
durable, a cork disc would 
produce a reasonable base. 

(2) Pivot Cut a 1 cm length off the 

pointed end of a needle (0.1 cm 
diameter) • Drill a small hole 
(0.1 cm diameter) in the middle 
of the base and set the needle 
in the hole with epoxy resin 
so that it stands vertically, 
pointed end uppermost. 

(3) Cap Take a brass rod (0.5 cms long) 

and cut off a length of 0.5 cms. 
Holding the rod firmly in a 
clamp drill a hole (0.3 cms 
diameter , 0.3 cms deep) along 
the axis of the rod. 



- 137 - 



(4) Magnetic Needles 




Take two needles and cut each 
to about 2 cms long. If the 
needles are tapered determine 
the center of gravity of each 
by balancing the needles over 
another needle, which serves 
as a pivot. Mark in the 
positions of the centers of 
gravity of the needles. 



*\ 



<LC 



$*> 




$.\^ r 



Hold the needles parallel to 
one another and drop some solder 
on the base of the cap. Attach 
the needles to the cap at their 
centers of gravity by placing 
them in the still molten solder. 

Finally, place the cap and 
needles inside a magnetizing 
coil (see 5.10/06) to magnetize 
them, and then place the cap 
on top of the pivot. 

Note the ends of the needles 
which point to the North, 
and mark these (e.g., with 
paint) . 



- 138 - 



5.10/06 Magnetizing Coil and Magnets 






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(1) Base 



(2) Spool 



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Cut the base out of wood 
(15 x 15 x 2 cms). 

Take a wooden dowel (a 
broomstick of diameter 3 cms) 
and cut off a length of 8 cms. 
Drill a hole (diameter 2 cms) 
along its axis. 



139 - 



(3) Endpleces 



(4) Magnet Wire 




Cut the endpieces (8 x 8 x 
0.5 cms) out of wood. Drill 
a hole (2 cms diameter) in the 
middle of each endpiece. Use 
wood cement to attach the 
endpieces to either end of 
the spool. 

Obtain 1 kilo of magnet wire 
(#22) and wind it all onto the 
spool (see notes) taking care 
to leave about 25 cms of both 
ends of the wire free to make 
appropriate connections. Drill 
a small hole in each endpiece 
and loop the wire ends through 
these holes to prevent un- 
winding of the coil. 

Make two insets (8 cms long, 
0.5 cms wide, 0.2 cms deep) 
in appropriate positions of 
the base to hold the endpieces. 
Use wood cement to fix the 
endpieces firmly in the insets. 



- 140 - 



(5) Electrical Connections 



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Connect one of the loose wires 
from the coil to a switch 
(attached to the base) and the 
other wire to a screw (in the 
base) o Connect one wire from 
a 2 meter length of parallel 
electrical cord (#20) to the 
screw, and the other wire to 
the free end of the switch. 

^ 2 msJui 



Attach a plug to the parallel 
cord. 

Cover all the magnet wire (the 
whole coil and the screw) with 
insulating tape to act as a 
safety measure. (It does in 
fact make good sense to pass 
the wire from the coil to the 
underside of the base to make 
the connections below, rather 
than above, the base). 

Notes : 

(i) To magnetize an item, Place a suitable steel specimen in the center 
of the coil. Switch the current quickly on and off. The specimen will be 
magnetized on removal from the coil. 

Ticonal is an ideal alloy for making magnets, but is rarely available on 
local markets. High quality tool steel is a good second best, and is generally 
found in good quality tools (chisels, screwdrivers, drill bits, etc e ), as well 
as domestic items such as razor blades and sewing needles. 

Unfortunately, the "high grade steel" sold on many local markets tends to 
be of poor quality, and does not retain magnetism well. However, if the steel 
is heated to red heat in an oxy-actylene flame, and then quenched in cold water, 



- 141 - 

it tends to be hardened, and hold magnetism somewhat better. (It should be 
noted that "steel rods" used in construction work for reinforcing concrete 
is a very soft iron, and cannot be permanently magnetized. 

This magnetizing coil is designed for use with 220 volt mains supply, 
and is capable of producing extremely strong magnets. It would also work 
with a 110 volt supply, but the magnetism induced in a given specimen would 
be weaker than with a 220 volt supply. The magnetizing coil should never be 
switched on and left on, as it would overheat and burn out. It is designed 
for usage over very short periods of time (2 or 3 seconds only) . 

To demagnetize a specimen, place the magnet inside the coil and hold 

its end very firmly. Switch on the current, and remove the specimen from the 

coil maintaining a firm grip on it. The current is not switched off until the 
specimen is completely out of the coil. 

(ii) The winding of the spool may be facilitated by the use of a brace. 
Hammer two large nails (15 cms long, 0.7 cms diameter) into the side of a 
bench so that they protrude horizontally some 50 cms apart. Place the spool 
to be wound on one of the nails. Fasten the first turn of magnet wire around 
the spool in such a way that it will not slip on turning the spool. Then get 
your partner to hold the wire taut over the second nail so that it may be 
wound under tension. 

Attach a short shaft (15 cms long, 1 cm diameter) to the center of a 
circular disc (7 cms diameter, 0.5 cms thick) by means of a central screw 
and wood cement. Hammer 3 nails through the perimeter of the disc and drill 
3 corresponding holes in the endpiece of the spool to take the protruding nails 



- 142 - 




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l^bCLOt. 



Clamp the jaws of the brace firmly on to the shaft, 
Lock the disc and spool together by means of the 
disc nails, and then begin to wind the coil by 
turning the brace. 



- 143 - 



5.10/07 Tangent Galvanometer 



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(1) Box Support 




Bok. \W\v 



Make a 4 sided wooden support 
from a base (12 x 6 x 1 cm) , 
2 sides (each 6x2x1 cm) 
and a top platform (12 x 6 
x 1 cm) . Fasten the base and 
sides together with small 
screws and wood cement, but do 
not put the platform in position 
yet. 

Drill an inset (0.2 cms deep) 
into the middle of the platform, 
and two holes right through- 
the platform to take the coil. 
Cut the platform into two equal 



J^S^V 



- 144 - 




halves fastening one half only 
in position with small screws 
and wood cement. 



(2) Coil 






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Ji'cWli 




To make the coil (100 turns, 
#24 magnet wire) a simple 
winding device is desirable. 
This may be made from a block 
of wood (5x5x1 cm) and 
two hardboard sides (8 x 8 x 0.5 
cms). Drill a hole through the 
middle of the block and sides 
and hold the parts together 
with a bolt and wingnut. 

Wind the magnet wire on to the 
block layer by layer, adding 
a coat of varnish to each layer 
to hold the turns together. 
Wind 100 turns on the block, 
and make sure that about 20 cms 
of both ends of the wire are 
left free to make the appropriate 
connections. 



- 145 - 



PLYfc*i* 




When the varnish is dry remove 
the coil from the block 
(simply by releasing the sides) 
and sit the coil vertically 
on the base. 

Attach the second half of the 
platform with small woodscrews 
and wood cen«nt. 



(3) Terminals 



(4) Compass 



Two terminals (de«cribed under 
5.10/01) are required. Fix 
one on either side of the box 
support, and attach the two 
wires from the c#il to the 
terminals. Don't forget to 
clean the *nd« of the wire 
with sandpaper. 

Place the compas* (described 
under 5.10/05) in th* inset 
on the platform* 



- 146 - 



5.10/08 Magnetic Field Apparatus 



2 



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(1) Base 

(2) Upright 



Make the base out of wood 
(10 x 7 x 1 cms) . 

Attach the wooden upright 
(11 x 4 x 2 cms) vertically 
to the base with two wooden 
screws passed through the base 
(4 ens from one end) . Use 
wood cement to insure a firm 
joint between the upright 
and base. 



- 147 - 



(3) Terminals 



(4) Rails 







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Two terminals (described under 
5.10/01) are required. Screw 
these into the base behind the 
vertical support. 

Cut two rails (each 5 cms long) 
from a brass rod (0,3 cms 
diameter) . Cut a thread on the 
end of each rod and find a nut 
to fit each. 

Drill two horizontal holes 
(0.3 cms diameter, 2.0 cms 
apart) through the support to 
take the rods. It is important 
that these two holes should be 
exactly at the same height 
(6 cms) above the base, and 
exactly horizontal. Pass the 
rails through the support. 
A little epoxy resin will hold 
the rails firmly in position, 
but avoid getting the resin 
(an insulator) on the protruding 
rails or threads. Attach the 
nuts to the protruding threads 
of the rails . 

Connect the terminals to the 
above nuts with magnet wire 
(#24). 



- 148 



(5) Roller 



(6) Magnet 



(7) Adjustment Screw 




The roller must be very light. 
Cut an aluminum rod (4 cms 
long, 0.3 cms diameter) for 
this purpose. 

A strong horseshoe magnet may- 
be handheld in the position 
illustrated to create a vertical 
magnetic field at right angles 
to the horizontal rails. 

Drill a hole (diameter 0.3 cms) 
through the base to take a 
bolt (2.0 cms long, 0.2 cms 
diameter) . Inset a correspond- 
ing nut over the hole by striking 
it into position with a hammer. 
Thread the bolt through the 
nut. 



Two similar adjustment screws 
at the opposite corners of the 
base would make the levelling 
of the apparatus simpler. 

Notes : 

(x) Should there be any difficulty in obtaining a good strong horseshoe 
magnet then multipurpose coils may be used instead, as described in the next 
item. 



- 149 - 



5.10/09 Magnetic Field Apparatus with Multipurpose Coils 



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(1) Base and Support 



This is the foregoing magnetic 
field apparatus (5.10/08) 
with the magnet removed. 
The components mentioned 
below enable the setting up 
of an electromagnetic field 
to replace that created by 
the horseshoe magnet. 



- 150 - 



(2) Multipurpose Coils 



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Two multipurpose coils complete 
with poleheads (see 5.10/04) 
are required. Cut a horizontal 
groove in the front endpiece 
of each, just beneath the 
poleheads, to insure a good 
grip for the coil holders. 



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(3) Coil Holders 





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Cut a sheet of brass (2 x 2 x 
0.2 cms), and make two spring 
holders. Attach these 
horizontally to the vertical 
support 1 cm above, and 1 cm 
below, the horizontal rails. 
Clip the multipurpose coils 
temporarily in the spring 
holders, and mark out the 
positions for the clip 
holders at the opposite end 
of each coil. 

Cut 4 clip holders (3.0 x 0.8 
x 0.05 cms) from a thin brass 
sheet. Cut the top off the 
vertical support so that this 
is level with the top of the 
upper coil. Take two clips, 
and fasten the slotted end of 
each under the locking nut of 
a terminal on the top end of 
the coil e Then holding the 
coil close to the support, 
attach the clips to the support 
with small screws. 



- 151 - 



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The two remaining clips must 
be bent to hold the bottom end 
of the lower coil. Measure 
the distance from the center 
of the terminal to the support. 
Let's say this is 1 cm, then 
the clips must be bent at 
right angles at 1.3 cms from 
the slotted end. Fit the 
slotted end of each clip under 
the locking nut of a terminal 
on the lower coil, and then 
screw the clips to the vertical 
support. 



- 152 - 



XocVi/ 




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(4) Terminals 



Two terminals (described under 
5.10/01) should be attached to 
the front of the base. 

Finally connect the terminals and 
coil holders by magnet wire 
(#24) so that electrical 
connections exist between points 
A to A, B to B and C to C (see 
above diagram) , thus insuring 
that current will flow through 
the multipurpose coils in the 
same direction once the 
terminals at the front of the 
base are connected to a circuit. 



- 153 



5.10/10 Moving Coil Galvanometer 



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(1) Base with Upright 



Cut the base out of wood 
(14 x 11 x 1 cm). Attach the 
wooden upright (6 x 11 x 1 cm) 
to the base with two screws 
from beneath the base and with 
wood cement to make a firm 
joint. Leave enough room 
(2 cms) behind the upright to 
permit space for two terminals 
to be fitted. 



- 154 - 



(2) Magnet 




Make an adjustment screw (as 
described under 5.10/08) to fit 
in one side of the base. 
Similar screws could well be 
placed at the two opposite 
corners of the base for more 
accurate levelling of the 
apparatus. 

Obtain a strong horseshoe magnet 
in which the separation of the 
two sides of the horseshoe is 
approximately 3 cms (or a 
little more). Make slots in 
the upright as illustrated to 
allow the magnet to be pushed 
through the upright so as to 
protrude a distance of 2 cms. 
Once the moving coil (below) 
has been fixed finally in 
position fix the magnet 
firmly in the upright with 
epoxy resin. 



(3) Moving Coil 



Xr\seT 




Cut a wooden core 3 cms long 
from a dowel (2 cms diameter). 
Make an inset (0.5 cms wide, 
0.5 cms deep) around the core 
specifically to hold a coil. 
Drill a hole (0.8 cms diameter) 
along the axis to take the pivot 
and soft iron core. 



- 155 - 






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Bore a hole (0,5 cms deep, 
0.1 cms diameter) horizontally 
into the bottom of the core at 
right angles to the plane of 
the inset (and coil). 

Then take a length of galvanized 
wire or aluminum (7.5 cms long, 
0.1 cms diameter) and fit it 
into the hole with epoxy resin 
to serve as a pointer. 

Obtain a needle (5 cms long, 
0.1 cm diameter) to serve as a 
pivot and a pile of nails 
(a little over 2 cms long and 
as small in diameter as possible} 
Cut off the nail heads and make 
the length 2 cms. Pack the 
nails into the hole through 
the middle of the wooden core, 
placing the needle in the 
very center of the hole, so as 
to protrude an equal distance 
either end of the core. Bind 
the newly created core and 
pivot firmly in position with 
a liberal coating of epoxy 
resin over the nail ends and 
around the needle. 



- 156 - 








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Wind 40 turns of magnet wire 
(No. 22) around the inset of 
the core, making sure that 
both ends are left free. 
Clean the ends of the wire 
with sandpaper and solder 
each end on to another length 
of very fine magnet wire 
(50 cms, No. 30) from which 
fine spring coils may be made 
around the top and bottom 
portions of the pivot according 
to the dimensions illustrated. 

Insert a wood screw into the 
base at a point 2 cms from the 
front of the upright and 5.5 cms 
from either side. Drill an 
inset (0.2 cms deep) into 
the head of the screw so that 
it will serve as a lower pivot 
for the coil. 



157 



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Bend a strip of brass 
(3.5 x 1.0 cm) to form an 
L shape. Drill a screw 
hole (diameter 0.3 cms) in 
the short end and a pivot hole 
(diameter 0,2 cms) at a 
distance of 0.5 cms from the 
other end. Slide the strip 
over the pivot needle, and 
screw the strip to the 
upright. 




- 158 - 

(4) Terminals Fit two terminals (as des- 

cribed under 5.10/01) into 
the front of the base. 
Connect the wire from the 
two ends of the springs to 
the two terminals. One of 
the best ways of doing this 
is to drill small holes in 
the upright (opposite the 
springs) threading the 
wire through the holes. If 
two more holes are drilled 
through the upright (one on 
either side) the wire may be 
threaded back through the 
upright to the terminals. 

(5) Scale Cut a sheet of paper and paste 

it on the base. Taking the 
lower pivot as the center 
point mark off a scale to 
indicate every 10 degree 
movement of the pointer. 
The scale may later be 
recalibrated in amps or 
volts as desired. 

Notes : 

(i) Should there be any difficulty in obtaining a suitable, strong 
horseshoe magnet then multipurpose coils may be used as described in the 
next item. 



159 - 



5.10/11 Moving Coil Galvanometer with Multipurpose Coils 



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(1) Basic Apparatus 



This is the basic magnetic 
field apparatus (described 

under 5.10/10) with the 
horseshoe magnet removed. 



- 160 - 



(2) Multipurpose Coils 



(3) Coil Holders 





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Two multipurpose coils 
(described under 5.10/09), 
complete with soft iron cores 
and poleheads, are required. 

Cut 4 clip holders (3.0 x 0.8 
x 0.05 cms) from a thin brass 
sheet, making a screwhole one 
end and a small slit at the 
other. Fit the 4 clips 
under the locking nuts of 
the 4 terminals of the multi- 
purpose coils. Then position 
each coil in turn on the 
upright so that the polehead 
is at exactly the same height 
above the base as the moving 
coil core. In this position 
screw the clips firmly on to 
the edge of the upright. 



Core 



VWci; 



- 161 - 




M M 

n 
(4) Terminals and Wiring 




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Make two spring holders from a 
brass sheet (2 x 2 x 0.02 cms) 
and slip these on the free 
ends of the multipurpose coils 
to determine where they should 
be attached to the upright. 
Having marked in the position 
screw the holders on to the 
upright. 

Fix two additional terminals 
(described under 5.10/01) 
to the base, just behind the 
upright, and then connect the 
clips and terminals with magne 
wire (#24) so that electrical 
connections exist between 
points A to A, B to B, C to C, 
D to D and E to E, thus 
insuring that once the 
additional terminals are 
connected to a circuit the 
resultant current will flow 
through the two coils in the 
same direction. 



Note: 

Those with reasonable technical ability will probably prefer to make 
this item from a technical drawing. The next item is therefore a blue-print 
of an almost identical galvanometer with only minor modifications (e.g., in 
the making of the core) . 



- 162- 



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- 168 - 



5 . 20 /01 Neon Bulb Holer with Bulb 




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(1) Base 



(2) Terminals 



(3) Neon Bulb 



Cut the base from wood 
(7x3x1 cm) . 

Fit one terminal (described 
under 5.10/01) at either 
end of the base. 

Solder magnet wire (#24) 
to the neon bulb wires, and 
connect the newly extended 
wires to the terminals. 



5,20/02 Electricity Tester 



- 169 - 




(1) Internal Components 







Solder one of the wires from 
the neon bulb on to a wire 
from a 200,000 ohm resistor 
(purchased from any radio 
shop) . Solder the other 
wire from the neon bulb to the 
metallic end of a screwdriver. 



(2) External Tube 



Select a plastic tube, which 
has the same diameter as that 
of the screwdriver end, and 
insert the newly joined 
components into the tube. 
Cut a piece of brass tubing 
(the same diameter as the 
tube- and 0,4 cms long) and 
solder the spare wire from 
the resistor on to this* 
Insert the brass tube into 
the end of the plastic tube. 



- 170 - 



5.20/03 Resistor Holder with Resistor 



i-a- — 




(1) Base 



(2) Terminals 



(3) Resistor 



Cut the base (7x3x1 cms) 
from wood. 

Fit two terminals (described 

under 5,10/01) to the base, 

one at either end. 
# 
Connect a 50 ohm resistor 

between the two terminals. 



r- 



5.20/04 Chemical Cell 



- 171 - 













(1) Container 



(2) Plates 



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Obtain a plastic, or glass, 
container, approximately 8 cms 
diameter and 8 cms deep, 
(A wide variety of electrolytes 
may be used, including commonly 
available vinegar and household 
salt solutions) . 

Cut alternative plates from 
zinc, copper and steel 
sheeting. Solder a brass 
suspension wire on to each. 
Also solder a similar 
suspension wire on to a 
carbon rod extracted from a 
dry cell. 



^ 



- 172 




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Cut two wooden holders (each 
approximately 10 x 1 x 1 cm) . 
In each drill a vertical 
suspension hole (0.2 cms 
diameter) and a horizontal 
bolt hole (0,3 cms diamter) 
to meet the vertical hole. 

Obtain a fitting bolt (0.3 cms 
diameter) and nut, and inset 
the nut over the bolt hole with 
a sharp tap of the hammer. 
(A little epoxy resin will 
hold the nut permanently 
in position) ♦ Thread a 
second nut onto the bolt to 
serve as a locking nut, and 
then screw the bolt into the 
bolt hole. Insert a suspension 
wire in the vertical hole, 
and clamp it in position by 
tightening the bolt. 

Electrical leads may be 
fastened under the locking 
nuts on the holders,, and the 
cell connected into an 
electrical circuit.